When processing log, we need to express the time in its local timezone for correlation.
most of the time we don’t need te fancy datetime and time is good enough for us.
from time import (tzset,
strptime, strftime,
mktime,
localtime, gmtime,
struct_time)
from calendar import timegm
format = "%Y-%m-%dT%H:%M:%S%p"
#os.environ['TZ'] = "US/Pacific"
#tzset()
ts = "2017-01-23T11:43:40PM"
st = strptime(ts, format)
# as local time
print("%s => %d" % (ts, mktime(st)))
# 2017-01-23T11:43:40PM => 1485200620
# as utc time
print("%s => %d" % (ts, timegm(st)))
# 2017-01-23T11:43:40PM => 1485171820
epoc = 1485200620
# to local time
t = localtime(epoc)
print("%d => %s" % (epoc, strftime(format, t)))
# 1485200620 => 2017-01-23T11:43:40AM
# to utc time
t = gmtime(epoc)
print("%d => %s" % (epoc, strftime(format, t)))
# 1485200620 => 2017-01-23T19:43:40PM
# manipulate struct_time
tl = list(t)
tl[0] = 2018
t = struct_time(tl)
print("=> %s" % strftime(format, t))
#=> 2018-01-23T19:43:40PM
from time import localtime, tzset, gmtime, strptime
from calendar import timegm
timezones = ["Asia/Shanghai", "America/Los_Angeles", "GMT"]
for tz in timezones:
os.environ['TZ'] = tz
tzset()
for time_str in (
"2017-01-23T11:43:40PM", # daylight saving time
"2017-04-23T11:43:40PM"
):
st = strptime(time_str, "%Y-%m-%dT%H:%M:%S%p")
as_local = mktime(st)
as_utc = timegm(st)
offset = as_utc - as_local
print("%s => UTC %+03d%02d" % (tz, offset/60/60, offset/60%30))
#Asia/Shanghai => UTC +0800
#Asia/Shanghai => UTC +0800
#America/Los_Angeles => UTC -0800
#America/Los_Angeles => UTC -0700
#GMT => UTC +0000
#GMT => UTC +0000