I need to store a timestamp in a readable format, and then later on I need to convert it to epoch for comparison purposes.
I tried doing this:
import time
format = '%Y %m %d %H:%M:%S +0000'
timestamp1 = time.strftime(format,time.gmtime()) # '2016 03 25 04:06:22 +0000'
t1 = time.strptime(timestamp1, format) # time.struct_time(..., tm_isdst=-1)
time.sleep(1)
epoch_now = time.mktime(time.gmtime())
epoch_t1 = time.mktime(t1)
print "Delta: %s" % (epoch_now - epoch_t1)
Running this, instead of getting Delta of 1 sec, I get 3601 (1 hr 1 sec), CONSISTENTLY.
Investigating further, it seems that when I just do time.gmtime(), the struct has tm_isdst=0, whereas the converted struct t1 from timestamp1 string has tm_isdst=-1.
How can I ensure the isdst is preserved to 0. I think that's probably the issue here.
Or is there a better way to record time in human readable format (UTC), and yet be able to convert back to epoch properly for time diff calculation?
UPDATES: After doing more research last night, I switched to using datetime because it preserves more information in the datetime object, and this is confirmed by albertoql answer below.
Here's what I have now:
from datetime import datetime
format = '%Y-%m-%d %H:%M:%S.%f +0000' # +0000 is optional; only for user to see it's UTC
d1 = datetime.utcnow()
timestamp1 = d1.strftime(format)
d1a = datetime.strptime(timestamp1, format)
time.sleep(1)
d2 = datetime.utcnow()
print "Delta: %s" % (d2 - d1a).seconds
I chose not to add tz to keep it simple/shorter; I can still strptime that way.