Question

In the code below, I am calculating now epoch and beginning of current day epoch.

import time
import pytz
from datetime import datetime

tz1 = pytz.timezone('CST6CDT')
utc = pytz.timezone('UTC')
now = pytz.UTC.localize(datetime.utcnow())
now_tz = now.astimezone(tz1)
print now_tz
print now_tz.strftime('%s')

begin_day = now_tz.replace(hour=0, minute=0, second=0)
print begin_day

print begin_day.strftime('%s')

print statements:

2012-08-28 13:52:21.595718-05:00
1346187141
2012-08-28 00:00:00.595718-05:00
1346137200

Converting epochs to timestamp with CDT timezone:
1346187141 – Aug 28 2012 15:52:21,
1346137200 – Aug 28 2012 02:00:00

I’d like the second epoch to be beginning of the day but it’s 2 am. It looks like it is still using local timezone PST when converting to epoch.

What am I doing wrong ? or can this be done a different way?

Thanks!

Answer 1

NOTE: My answer is flat-out wrong. (I’d like to delete it, but am unable to do so until the accept flag is removed.)

Please see J.F.Sebastian’s answer.

Here is code demonstrating a value of now_tz for which our two methods produce different results.

import calendar
import pytz
import datetime as dt

tz1 = pytz.timezone('US/Eastern')
utc = pytz.timezone('UTC')
now = utc.localize(dt.datetime(2002, 10, 28), is_dst=None)
now_tz = now.astimezone(tz1)
now_epoch = calendar.timegm(now_tz.utctimetuple())
begin_day = tz1.normalize(now_tz.replace(hour=0, minute=0, second=0))

midnight = tz1.localize(dt.datetime.combine(now_tz, dt.time(0, 0)), is_dst=None)
if begin_day != midnight:
    print(begin_day)
    # 2002-10-27 01:00:00-04:00  # my result -- is not midnight
    print(midnight)
    # 2002-10-27 00:00:00-04:00  # J.F.Sebastian's result is correct

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(Original answer redacted)