python-relative-time

relative_time.py

from datetime import datetime, timedelta


def relative_time(date):
    """Take a datetime and return its "age" as a string.

    The age can be in second, minute, hour, day, month or year. Only the
    biggest unit is considered, e.g. if it's 2 days and 3 hours, "2 days" will
    be returned.

    Make sure date is not in the future, or else it won't work.

    Original Gist by 'zhangsen' @ https://gist.github.com/zhangsen/1199964
    """

    def formatn(n, s):
        """Add "s" if it's plural"""

        if n == 1:
            return "1 %s" % s
        elif n > 1:
            return "%d %ss" % (n, s)

    def qnr(a, b):
        """Return quotient and remaining"""

        return a / b, a % b

    class FormatDelta:

        def __init__(self, dt):
            now = datetime.now()
            delta = now - dt
            self.day = delta.days
            self.second = delta.seconds
            self.year, self.day = qnr(self.day, 365)
            self.month, self.day = qnr(self.day, 30)
            self.hour, self.second = qnr(self.second, 3600)
            self.minute, self.second = qnr(self.second, 60)

        def format(self):
            for period in ['year', 'month', 'day', 'hour', 'minute', 'second']:
                n = getattr(self, period)
                if n >= 1:
                    return '{0} ago'.format(formatn(n, period))
            return "just now"

    return FormatDelta(date).format()


#
# EXAMPLES
#

just_now = relative_time(datetime.now())  # >>> just now
ten_years_ago = relative_time(datetime(2008, 9, 1))  # >>> 11 years ago
six_years_ago = relative_time(datetime.now() - timedelta(days=6))  # >>> 6 days ago
twenty_minutes = relative_time(datetime.now() - timedelta(minutes=20))  # >>> 20 minutes ago

print('')
print('just now............: {0}'.format(just_now))
print('ten years ago.......: {0}'.format(ten_years_ago))
print('six years ago.......: {0}'.format(six_years_ago))
print('twenty minutes ago..: {0}'.format(twenty_minutes))

This code is good except on line 44 I found that n can be a decimal, making n > 0 pass but formatn() still not return anything, making certain strings show up as None ago.
Line 44 should be if n >= 1 to fix this problem. Also, you might want to put an else in formatn() on line 23 that raises an error so as to not silently return None.

Gist updated... thanks @Scoder12!