Convert a string date to a timestamp

Question

Is there any simple way to convert a RFC HTTP date into a timestamp in Lua?

"Sat, 29 Oct 1994 19:43:31 GMT"

into

783467011

Answer 1

Correcting lhf's example code to account for timezone since os.time() does not have a way to specify the timezone. Also assume all input ends in GMT since this only works with GMT.

s="Sat, 29 Oct 1994 19:43:31 GMT"
p="%a+, (%d+) (%a+) (%d+) (%d+):(%d+):(%d+) GMT"
day,month,year,hour,min,sec=s:match(p)
MON={Jan=1,Feb=2,Mar=3,Apr=4,May=5,Jun=6,Jul=7,Aug=8,Sep=9,Oct=10,Nov=11,Dec=12}
month=MON[month]
offset=os.time()-os.time(os.date("!*t"))
print(os.time({day=day,month=month,year=year,hour=hour,min=min,sec=sec})+offset)

Which gives us 783477811. And we will verify with os.date("!%c") because the ! will make the output in UTC instead of local timezone.

print(os.date("!%c",783477811))
--> Sat Oct 29 19:43:31 1994

Answer 2

use luadate, you can install it with luarocks.

date = require 'date'
local d1 = date('Sat, 29 Oct 1994 19:43:31 GMT')                                                                                               
local seconds = date.diff(d1, date.epoch()):spanseconds()
print(seconds)