Convert from human readable date/time to epoch timestamp

datetime2epoch.lua

-- The MIT License (MIT)
-- Copyright (c) 2018,2020 Thomas Mohaupt <thomas.mohaupt@gmail.com>

-- year: 2-digit (means 20xx) or 4-digit (>= 2000)
function datetime2epoch(second, minute, hour, day, month, year)
  local mi2sec = 60
  local h2sec = 60 * mi2sec
  local d2sec = 24 * h2sec
  -- month to second, without leap year 
  local m2sec = {
        0, 
        31 * d2sec, 
        59 * d2sec, 
        90 * d2sec, 
        120 * d2sec, 
        151 * d2sec, 
        181 * d2sec, 
        212 * d2sec, 
        243 * d2sec, 
        273 * d2sec, 
        304 * d2sec, 
        334 * d2sec }  
        
  local y2sec = 365 * d2sec
  local offsetSince1970 = 946684800

  local yy = year < 100 and year or year - 2000

  local leapCorrection = math.floor(yy/4) + 1  
  if (yy % 4) == 0 and month < 3 then
    leapCorrection = leapCorrection - 1
  end
  
  return offsetSince1970 + 
        second + 
        minute * mi2sec + 
        hour * h2sec + 
        (day - 1) * d2sec + 
        m2sec[month] + 
        yy * y2sec +
        leapCorrection * d2sec 
end

-- datetime2epoch(11,12,13,7,9,20) 
-- 1599484331
-- datetime2epoch(11,12,13,7,9,2020)
-- 1599484331

datetime2epoch(11,12,13,7,9,2020) does not lead to a UNIX timestamp reflecting Sept. 7th, 2020 13:12:11 but instead 64714684331 which is
09/22/4020 @ 1:12pm (UTC). Test on nodemcu-firmware 3.0.0.0 with Lua 5.1.4.
So it seems to be off 2000 years + 15 days in this example.

datetime2epoch(11,12,13,7,9,2020) does not lead to a UNIX timestamp reflecting Sept. 7th, 2020 13:12:11 but instead 64714684331 which is
09/22/4020 @ 1:12pm (UTC). Test on nodemcu-firmware 3.0.0.0 with Lua 5.1.4.
So it seems to be off 2000 years + 15 days in this example.

Thanks for your feedback - it was mentioned to be used with 2-digit years (since 2000). I have changed it to also accept 4-digit years now.

Hello, thank you very much for the very quick fix! I can confirm that it works now as expected. Awesome! 👍