PM2Ring/leap-seconds.py

## leap-seconds.py
# Fetch & parse leap-seconds.list

from datetime import datetime, timezone, timedelta
from hashlib import sha1
import requests

# Leap second data source
# url = 'https://www.ietf.org/timezones/data/leap-seconds.list'
url = 'https://raw.githubusercontent.com/eggert/tz/main/leap-seconds.list'

mjd_epoch = datetime(year=1900, month=1, day=1, tzinfo=timezone.utc)

def from_ntp(secs):
    return mjd_epoch + timedelta(seconds=int(secs))

req = requests.get(url)
# print(req.text)
data = req.text.splitlines()
a = [s.split() for s in data]
a = [row for row in a if len(row)>1 and len(row[0])>1]

TAI = []
lsdata = []
for row in a:
    if row[0].startswith('#'):
        c = row[0][1]
        if c=='$':
            print('Last update', from_ntp(row[1]))
            lsdata.append(row[1])
        elif c=='@':
            print('Expires', from_ntp(row[1]))
            lsdata.append(row[1])
        elif c=='h':
            hashstamp = row[1:]
            print('File hash', ' '.join(hashstamp))
        else:
            print('Bogus special comment!', repr(' '.join(row)))
    else:
        print(' '.join(row))
        lsdata.extend(row[:2])
        TAI.append([int(u) for u in row[:2]])

# hashstamp drops leading zeroes!
hashstamp = ''.join([u.rjust(8, '0') for u in hashstamp])
print(' '*9, hashstamp)

newhash = sha1(''.join(lsdata).encode('ascii')).hexdigest()
print('Our hash ', newhash)
print('Hashes match:', hashstamp==newhash)
print()
print('TAI = [', *[f'    {row},' for row in TAI], ']', sep="\n")

## leapseconds1.py
# Fetch & parse leap-seconds.list

from datetime import datetime, timezone, timedelta
from hashlib import sha1
import requests

# leap-seconds.list sources
# Obsolete IETF
#url = 'https://www.ietf.org/timezones/data/leap-seconds.list'
# IANA
url = 'https://raw.githubusercontent.com/eggert/tz/main/leap-seconds.list'
#url = 'https://data.iana.org/time-zones/data/leap-seconds.list'
# IERS, the primary source
#url = 'https://hpiers.obspm.fr/iers/bul/bulc/ntp/leap-seconds.list'

mjd_epoch = datetime(year=1900, month=1, day=1, tzinfo=timezone.utc)

def from_ntp(secs):
    return mjd_epoch + timedelta(seconds=int(secs))

def fetch_leapsecs(url):
    print("Fetching", url, "...")
    try:
        req = requests.get(url, timeout=4)
    except OSError as err:
        print("Can't connect!")
        print(err)
        return None

    # print(req.text)
    print("Ok")

    data = req.text.splitlines()
    a = [s.split() for s in data]
    a = [row for row in a if len(row)>1 and len(row[0])>1]

    TAI = []
    lsdata = []
    for row in a:
        if row[0].startswith('#'):
            c = row[0][1]
            if c=='$':
                print('Last update', from_ntp(row[1]))
                lsdata.append(row[1])
            elif c=='@':
                print('Expires', from_ntp(row[1]))
                lsdata.append(row[1])
            elif c=='h':
                hashstamp = row[1:]
                print('File hash', ' '.join(hashstamp))
            elif c=='N':
                # Data header line
                print('\n' + ' '.join(row)[1:])
            else:
                print('Bogus special comment!', repr(' '.join(row)))
        else:
            print(' '.join(row))
            lsdata.extend(row[:2])
            TAI.append([int(u) for u in row[:2]])

    # hashstamp drops leading zeroes!
    hashstamp = ''.join([u.rjust(8, '0') for u in hashstamp])
    print(' '*9, hashstamp)

    newhash = sha1(''.join(lsdata).encode('ascii')).hexdigest()
    print('Our hash ', newhash)
    print('Hashes match:', hashstamp==newhash)
    print()
    return TAI

TAI = fetch_leapsecs(url)
if TAI is not None:
    print('TAI = [', *[f'    {row},' for row in TAI], ']', sep="\n")

## old-leap-seconds.list
#
#	In the following text, the symbol '#' introduces
#	a comment, which continues from that symbol until
#	the end of the line. A plain comment line has a
#	whitespace character following the comment indicator.
#	There are also special comment lines defined below.
#	A special comment will always have a non-whitespace
#	character in column 2.
#
#	A blank line should be ignored.
#
#	The following table shows the corrections that must
#	be applied to compute International Atomic Time (TAI)
#	from the Coordinated Universal Time (UTC) values that
#	are transmitted by almost all time services.
#
#	The first column shows an epoch as a number of seconds
#	since 1 January 1900, 00:00:00 (1900.0 is also used to
#	indicate the same epoch.) Both of these time stamp formats
#	ignore the complexities of the time scales that were
#	used before the current definition of UTC at the start
#	of 1972. (See note 3 below.)
#	The second column shows the number of seconds that
#	must be added to UTC to compute TAI for any timestamp
#	at or after that epoch. The value on each line is
#	valid from the indicated initial instant until the
#	epoch given on the next one or indefinitely into the
#	future if there is no next line.
#	(The comment on each line shows the representation of
#	the corresponding initial epoch in the usual
#	day-month-year format. The epoch always begins at
#	00:00:00 UTC on the indicated day. See Note 5 below.)
#
#	Important notes:
#
#	1. Coordinated Universal Time (UTC) is often referred to
#	as Greenwich Mean Time (GMT). The GMT time scale is no
#	longer used, and the use of GMT to designate UTC is
#	discouraged.
#
#	2. The UTC time scale is realized by many national
#	laboratories and timing centers. Each laboratory
#	identifies its realization with its name: Thus
#	UTC(NIST), UTC(USNO), etc. The differences among
#	these different realizations are typically on the
#	order of a few nanoseconds (i.e., 0.000 000 00x s)
#	and can be ignored for many purposes. These differences
#	are tabulated in Circular T, which is published monthly
#	by the International Bureau of Weights and Measures
#	(BIPM). See www.bipm.org for more information.
#
#	3. The current definition of the relationship between UTC
#	and TAI dates from 1 January 1972. A number of different
#	time scales were in use before that epoch, and it can be
#	quite difficult to compute precise timestamps and time
#	intervals in those "prehistoric" days. For more information,
#	consult:
#
#		The Explanatory Supplement to the Astronomical
#		Ephemeris.
#	or
#		Terry Quinn, "The BIPM and the Accurate Measurement
#		of Time," Proc. of the IEEE, Vol. 79, pp. 894-905,
#		July, 1991. <http://dx.doi.org/10.1109/5.84965>
#		reprinted in:
#		   Christine Hackman and Donald B Sullivan (eds.)
#		   Time and Frequency Measurement
#		   American Association of Physics Teachers (1996)
#		   <http://tf.nist.gov/general/pdf/1168.pdf>, pp. 75-86
#
#	4. The decision to insert a leap second into UTC is currently
#	the responsibility of the International Earth Rotation and
#	Reference Systems Service. (The name was changed from the
#	International Earth Rotation Service, but the acronym IERS
#	is still used.)
#
#	Leap seconds are announced by the IERS in its Bulletin C.
#
#	See www.iers.org for more details.
#
#	Every national laboratory and timing center uses the
#	data from the BIPM and the IERS to construct UTC(lab),
#	their local realization of UTC.
#
#	Although the definition also includes the possibility
#	of dropping seconds ("negative" leap seconds), this has
#	never been done and is unlikely to be necessary in the
#	foreseeable future.
#
#	5. If your system keeps time as the number of seconds since
#	some epoch (e.g., NTP timestamps), then the algorithm for
#	assigning a UTC time stamp to an event that happens during a positive
#	leap second is not well defined. The official name of that leap
#	second is 23:59:60, but there is no way of representing that time
#	in these systems.
#	Many systems of this type effectively stop the system clock for
#	one second during the leap second and use a time that is equivalent
#	to 23:59:59 UTC twice. For these systems, the corresponding TAI
#	timestamp would be obtained by advancing to the next entry in the
#	following table when the time equivalent to 23:59:59 UTC
#	is used for the second time. Thus the leap second which
#	occurred on 30 June 1972 at 23:59:59 UTC would have TAI
#	timestamps computed as follows:
#
#	...
#	30 June 1972 23:59:59 (2287785599, first time):	TAI= UTC + 10 seconds
#	30 June 1972 23:59:60 (2287785599,second time):	TAI= UTC + 11 seconds
#	1  July 1972 00:00:00 (2287785600)		TAI= UTC + 11 seconds
#	...
#
#	If your system realizes the leap second by repeating 00:00:00 UTC twice
#	(this is possible but not usual), then the advance to the next entry
#	in the table must occur the second time that a time equivalent to
#	00:00:00 UTC is used. Thus, using the same example as above:
#
#	...
#       30 June 1972 23:59:59 (2287785599):		TAI= UTC + 10 seconds
#       30 June 1972 23:59:60 (2287785600, first time):	TAI= UTC + 10 seconds
#       1  July 1972 00:00:00 (2287785600,second time):	TAI= UTC + 11 seconds
#	...
#
#	in both cases the use of timestamps based on TAI produces a smooth
#	time scale with no discontinuity in the time interval. However,
#	although the long-term behavior of the time scale is correct in both
#	methods, the second method is technically not correct because it adds
#	the extra second to the wrong day.
#
#	This complexity would not be needed for negative leap seconds (if they
#	are ever used). The UTC time would skip 23:59:59 and advance from
#	23:59:58 to 00:00:00 in that case. The TAI offset would decrease by
#	1 second at the same instant. This is a much easier situation to deal
#	with, since the difficulty of unambiguously representing the epoch
#	during the leap second does not arise.
#
#	Some systems implement leap seconds by amortizing the leap second
#	over the last few minutes of the day. The frequency of the local
#	clock is decreased (or increased) to realize the positive (or
#	negative) leap second. This method removes the time step described
#	above. Although the long-term behavior of the time scale is correct
#	in this case, this method introduces an error during the adjustment
#	period both in time and in frequency with respect to the official
#	definition of UTC.
#
#	Questions or comments to:
#		Judah Levine
#		Time and Frequency Division
#		NIST
#		Boulder, Colorado
#		Judah.Levine@nist.gov
#
#	Last Update of leap second values:   8 July 2016
#
#	The following line shows this last update date in NTP timestamp
#	format. This is the date on which the most recent change to
#	the leap second data was added to the file. This line can
#	be identified by the unique pair of characters in the first two
#	columns as shown below.
#
#$	 3676924800
#
#	The NTP timestamps are in units of seconds since the NTP epoch,
#	which is 1 January 1900, 00:00:00. The Modified Julian Day number
#	corresponding to the NTP time stamp, X, can be computed as
#
#	X/86400 + 15020
#
#	where the first term converts seconds to days and the second
#	term adds the MJD corresponding to the time origin defined above.
#	The integer portion of the result is the integer MJD for that
#	day, and any remainder is the time of day, expressed as the
#	fraction of the day since 0 hours UTC. The conversion from day
#	fraction to seconds or to hours, minutes, and seconds may involve
#	rounding or truncation, depending on the method used in the
#	computation.
#
#	The data in this file will be updated periodically as new leap
#	seconds are announced. In addition to being entered on the line
#	above, the update time (in NTP format) will be added to the basic
#	file name leap-seconds to form the name leap-seconds.<NTP TIME>.
#	In addition, the generic name leap-seconds.list will always point to
#	the most recent version of the file.
#
#	This update procedure will be performed only when a new leap second
#	is announced.
#
#	The following entry specifies the expiration date of the data
#	in this file in units of seconds since the origin at the instant
#	1 January 1900, 00:00:00. This expiration date will be changed
#	at least twice per year whether or not a new leap second is
#	announced. These semi-annual changes will be made no later
#	than 1 June and 1 December of each year to indicate what
#	action (if any) is to be taken on 30 June and 31 December,
#	respectively. (These are the customary effective dates for new
#	leap seconds.) This expiration date will be identified by a
#	unique pair of characters in columns 1 and 2 as shown below.
#	In the unlikely event that a leap second is announced with an
#	effective date other than 30 June or 31 December, then this
#	file will be edited to include that leap second as soon as it is
#	announced or at least one month before the effective date
#	(whichever is later).
#	If an announcement by the IERS specifies that no leap second is
#	scheduled, then only the expiration date of the file will
#	be advanced to show that the information in the file is still
#	current -- the update time stamp, the data and the name of the file
#	will not change.
#
#	Updated through IERS Bulletin C60
#	File expires on:  28 June 2021
#
#@	3833827200
#
2272060800	10	# 1 Jan 1972
2287785600	11	# 1 Jul 1972
2303683200	12	# 1 Jan 1973
2335219200	13	# 1 Jan 1974
2366755200	14	# 1 Jan 1975
2398291200	15	# 1 Jan 1976
2429913600	16	# 1 Jan 1977
2461449600	17	# 1 Jan 1978
2492985600	18	# 1 Jan 1979
2524521600	19	# 1 Jan 1980
2571782400	20	# 1 Jul 1981
2603318400	21	# 1 Jul 1982
2634854400	22	# 1 Jul 1983
2698012800	23	# 1 Jul 1985
2776982400	24	# 1 Jan 1988
2840140800	25	# 1 Jan 1990
2871676800	26	# 1 Jan 1991
2918937600	27	# 1 Jul 1992
2950473600	28	# 1 Jul 1993
2982009600	29	# 1 Jul 1994
3029443200	30	# 1 Jan 1996
3076704000	31	# 1 Jul 1997
3124137600	32	# 1 Jan 1999
3345062400	33	# 1 Jan 2006
3439756800	34	# 1 Jan 2009
3550089600	35	# 1 Jul 2012
3644697600	36	# 1 Jul 2015
3692217600	37	# 1 Jan 2017
#
#	the following special comment contains the
#	hash value of the data in this file computed
#	use the secure hash algorithm as specified
#	by FIPS 180-1. See the files in ~/pub/sha for
#	the details of how this hash value is
#	computed. Note that the hash computation
#	ignores comments and whitespace characters
#	in data lines. It includes the NTP values
#	of both the last modification time and the
#	expiration time of the file, but not the
#	white space on those lines.
#	the hash line is also ignored in the
#	computation.
#
#h 	064356a8 39268b92 76e4d5ef 3e22fae1 0cca529c
	# Fetch & parse leap-seconds.list

	from datetime import datetime, timezone, timedelta
	from hashlib import sha1
	import requests

	# Leap second data source
	# url = 'https://www.ietf.org/timezones/data/leap-seconds.list'
	url = 'https://raw.githubusercontent.com/eggert/tz/main/leap-seconds.list'

	mjd_epoch = datetime(year=1900, month=1, day=1, tzinfo=timezone.utc)

	def from_ntp(secs):
	return mjd_epoch + timedelta(seconds=int(secs))

	req = requests.get(url)
	# print(req.text)
	data = req.text.splitlines()
	a = [s.split() for s in data]
	a = [row for row in a if len(row)>1 and len(row[0])>1]

	TAI = []
	lsdata = []
	for row in a:
	if row[0].startswith('#'):
	c = row[0][1]
	if c=='$':
	print('Last update', from_ntp(row[1]))
	lsdata.append(row[1])
	elif c=='@':
	print('Expires', from_ntp(row[1]))
	lsdata.append(row[1])
	elif c=='h':
	hashstamp = row[1:]
	print('File hash', ' '.join(hashstamp))
	else:
	print('Bogus special comment!', repr(' '.join(row)))
	else:
	print(' '.join(row))
	lsdata.extend(row[:2])
	TAI.append([int(u) for u in row[:2]])

	# hashstamp drops leading zeroes!
	hashstamp = ''.join([u.rjust(8, '0') for u in hashstamp])
	print(' '*9, hashstamp)

	newhash = sha1(''.join(lsdata).encode('ascii')).hexdigest()
	print('Our hash ', newhash)
	print('Hashes match:', hashstamp==newhash)
	print()
	print('TAI = [', *[f' {row},' for row in TAI], ']', sep="\n")
	#
	# In the following text, the symbol '#' introduces
	# a comment, which continues from that symbol until
	# the end of the line. A plain comment line has a
	# whitespace character following the comment indicator.
	# There are also special comment lines defined below.
	# A special comment will always have a non-whitespace
	# character in column 2.
	#
	# A blank line should be ignored.
	#
	# The following table shows the corrections that must
	# be applied to compute International Atomic Time (TAI)
	# from the Coordinated Universal Time (UTC) values that
	# are transmitted by almost all time services.
	#
	# The first column shows an epoch as a number of seconds
	# since 1 January 1900, 00:00:00 (1900.0 is also used to
	# indicate the same epoch.) Both of these time stamp formats
	# ignore the complexities of the time scales that were
	# used before the current definition of UTC at the start
	# of 1972. (See note 3 below.)
	# The second column shows the number of seconds that
	# must be added to UTC to compute TAI for any timestamp
	# at or after that epoch. The value on each line is
	# valid from the indicated initial instant until the
	# epoch given on the next one or indefinitely into the
	# future if there is no next line.
	# (The comment on each line shows the representation of
	# the corresponding initial epoch in the usual
	# day-month-year format. The epoch always begins at
	# 00:00:00 UTC on the indicated day. See Note 5 below.)
	#
	# Important notes:
	#
	# 1. Coordinated Universal Time (UTC) is often referred to
	# as Greenwich Mean Time (GMT). The GMT time scale is no
	# longer used, and the use of GMT to designate UTC is
	# discouraged.
	#
	# 2. The UTC time scale is realized by many national
	# laboratories and timing centers. Each laboratory
	# identifies its realization with its name: Thus
	# UTC(NIST), UTC(USNO), etc. The differences among
	# these different realizations are typically on the
	# order of a few nanoseconds (i.e., 0.000 000 00x s)
	# and can be ignored for many purposes. These differences
	# are tabulated in Circular T, which is published monthly
	# by the International Bureau of Weights and Measures
	# (BIPM). See www.bipm.org for more information.
	#
	# 3. The current definition of the relationship between UTC
	# and TAI dates from 1 January 1972. A number of different
	# time scales were in use before that epoch, and it can be
	# quite difficult to compute precise timestamps and time
	# intervals in those "prehistoric" days. For more information,
	# consult:
	#
	# The Explanatory Supplement to the Astronomical
	# Ephemeris.
	# or
	# Terry Quinn, "The BIPM and the Accurate Measurement
	# of Time," Proc. of the IEEE, Vol. 79, pp. 894-905,
	# July, 1991. <http://dx.doi.org/10.1109/5.84965>
	# reprinted in:
	# Christine Hackman and Donald B Sullivan (eds.)
	# Time and Frequency Measurement
	# American Association of Physics Teachers (1996)
	# <http://tf.nist.gov/general/pdf/1168.pdf>, pp. 75-86
	#
	# 4. The decision to insert a leap second into UTC is currently
	# the responsibility of the International Earth Rotation and
	# Reference Systems Service. (The name was changed from the
	# International Earth Rotation Service, but the acronym IERS
	# is still used.)
	#
	# Leap seconds are announced by the IERS in its Bulletin C.
	#
	# See www.iers.org for more details.
	#
	# Every national laboratory and timing center uses the
	# data from the BIPM and the IERS to construct UTC(lab),
	# their local realization of UTC.
	#
	# Although the definition also includes the possibility
	# of dropping seconds ("negative" leap seconds), this has
	# never been done and is unlikely to be necessary in the
	# foreseeable future.
	#
	# 5. If your system keeps time as the number of seconds since
	# some epoch (e.g., NTP timestamps), then the algorithm for
	# assigning a UTC time stamp to an event that happens during a positive
	# leap second is not well defined. The official name of that leap
	# second is 23:59:60, but there is no way of representing that time
	# in these systems.
	# Many systems of this type effectively stop the system clock for
	# one second during the leap second and use a time that is equivalent
	# to 23:59:59 UTC twice. For these systems, the corresponding TAI
	# timestamp would be obtained by advancing to the next entry in the
	# following table when the time equivalent to 23:59:59 UTC
	# is used for the second time. Thus the leap second which
	# occurred on 30 June 1972 at 23:59:59 UTC would have TAI
	# timestamps computed as follows:
	#
	# ...
	# 30 June 1972 23:59:59 (2287785599, first time): TAI= UTC + 10 seconds
	# 30 June 1972 23:59:60 (2287785599,second time): TAI= UTC + 11 seconds
	# 1 July 1972 00:00:00 (2287785600) TAI= UTC + 11 seconds
	# ...
	#
	# If your system realizes the leap second by repeating 00:00:00 UTC twice
	# (this is possible but not usual), then the advance to the next entry
	# in the table must occur the second time that a time equivalent to
	# 00:00:00 UTC is used. Thus, using the same example as above:
	#
	# ...
	# 30 June 1972 23:59:59 (2287785599): TAI= UTC + 10 seconds
	# 30 June 1972 23:59:60 (2287785600, first time): TAI= UTC + 10 seconds
	# 1 July 1972 00:00:00 (2287785600,second time): TAI= UTC + 11 seconds
	# ...
	#
	# in both cases the use of timestamps based on TAI produces a smooth
	# time scale with no discontinuity in the time interval. However,
	# although the long-term behavior of the time scale is correct in both
	# methods, the second method is technically not correct because it adds
	# the extra second to the wrong day.
	#
	# This complexity would not be needed for negative leap seconds (if they
	# are ever used). The UTC time would skip 23:59:59 and advance from
	# 23:59:58 to 00:00:00 in that case. The TAI offset would decrease by
	# 1 second at the same instant. This is a much easier situation to deal
	# with, since the difficulty of unambiguously representing the epoch
	# during the leap second does not arise.
	#
	# Some systems implement leap seconds by amortizing the leap second
	# over the last few minutes of the day. The frequency of the local
	# clock is decreased (or increased) to realize the positive (or
	# negative) leap second. This method removes the time step described
	# above. Although the long-term behavior of the time scale is correct
	# in this case, this method introduces an error during the adjustment
	# period both in time and in frequency with respect to the official
	# definition of UTC.
	#
	# Questions or comments to:
	# Judah Levine
	# Time and Frequency Division
	# NIST
	# Boulder, Colorado
	# Judah.Levine@nist.gov
	#
	# Last Update of leap second values: 8 July 2016
	#
	# The following line shows this last update date in NTP timestamp
	# format. This is the date on which the most recent change to
	# the leap second data was added to the file. This line can
	# be identified by the unique pair of characters in the first two
	# columns as shown below.
	#
	#$ 3676924800
	#
	# The NTP timestamps are in units of seconds since the NTP epoch,
	# which is 1 January 1900, 00:00:00. The Modified Julian Day number
	# corresponding to the NTP time stamp, X, can be computed as
	#
	# X/86400 + 15020
	#
	# where the first term converts seconds to days and the second
	# term adds the MJD corresponding to the time origin defined above.
	# The integer portion of the result is the integer MJD for that
	# day, and any remainder is the time of day, expressed as the
	# fraction of the day since 0 hours UTC. The conversion from day
	# fraction to seconds or to hours, minutes, and seconds may involve
	# rounding or truncation, depending on the method used in the
	# computation.
	#
	# The data in this file will be updated periodically as new leap
	# seconds are announced. In addition to being entered on the line
	# above, the update time (in NTP format) will be added to the basic
	# file name leap-seconds to form the name leap-seconds.<NTP TIME>.
	# In addition, the generic name leap-seconds.list will always point to
	# the most recent version of the file.
	#
	# This update procedure will be performed only when a new leap second
	# is announced.
	#
	# The following entry specifies the expiration date of the data
	# in this file in units of seconds since the origin at the instant
	# 1 January 1900, 00:00:00. This expiration date will be changed
	# at least twice per year whether or not a new leap second is
	# announced. These semi-annual changes will be made no later
	# than 1 June and 1 December of each year to indicate what
	# action (if any) is to be taken on 30 June and 31 December,
	# respectively. (These are the customary effective dates for new
	# leap seconds.) This expiration date will be identified by a
	# unique pair of characters in columns 1 and 2 as shown below.
	# In the unlikely event that a leap second is announced with an
	# effective date other than 30 June or 31 December, then this
	# file will be edited to include that leap second as soon as it is
	# announced or at least one month before the effective date
	# (whichever is later).
	# If an announcement by the IERS specifies that no leap second is
	# scheduled, then only the expiration date of the file will
	# be advanced to show that the information in the file is still
	# current -- the update time stamp, the data and the name of the file
	# will not change.
	#
	# Updated through IERS Bulletin C60
	# File expires on: 28 June 2021
	#
	#@ 3833827200
	#
	2272060800 10 # 1 Jan 1972
	2287785600 11 # 1 Jul 1972
	2303683200 12 # 1 Jan 1973
	2335219200 13 # 1 Jan 1974
	2366755200 14 # 1 Jan 1975
	2398291200 15 # 1 Jan 1976
	2429913600 16 # 1 Jan 1977
	2461449600 17 # 1 Jan 1978
	2492985600 18 # 1 Jan 1979
	2524521600 19 # 1 Jan 1980
	2571782400 20 # 1 Jul 1981
	2603318400 21 # 1 Jul 1982
	2634854400 22 # 1 Jul 1983
	2698012800 23 # 1 Jul 1985
	2776982400 24 # 1 Jan 1988
	2840140800 25 # 1 Jan 1990
	2871676800 26 # 1 Jan 1991
	2918937600 27 # 1 Jul 1992
	2950473600 28 # 1 Jul 1993
	2982009600 29 # 1 Jul 1994
	3029443200 30 # 1 Jan 1996
	3076704000 31 # 1 Jul 1997
	3124137600 32 # 1 Jan 1999
	3345062400 33 # 1 Jan 2006
	3439756800 34 # 1 Jan 2009
	3550089600 35 # 1 Jul 2012
	3644697600 36 # 1 Jul 2015
	3692217600 37 # 1 Jan 2017
	#
	# the following special comment contains the
	# hash value of the data in this file computed
	# use the secure hash algorithm as specified
	# by FIPS 180-1. See the files in ~/pub/sha for
	# the details of how this hash value is
	# computed. Note that the hash computation
	# ignores comments and whitespace characters
	# in data lines. It includes the NTP values
	# of both the last modification time and the
	# expiration time of the file, but not the
	# white space on those lines.
	# the hash line is also ignored in the
	# computation.
	#
	#h 064356a8 39268b92 76e4d5ef 3e22fae1 0cca529c