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# Date Time conversions in python from a 64 bit timestamp.

Posted on 2010-11-27
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I am trying to convert a 64bit timestamp in to a human readable representation.

The last_visit_time field of the History.urls table in google-chromes History database is a 64bit timestamp.

The formula I use to convert to unix epoch time is :

unixepochtime  =      last_visit_time / 10000000L
datetime.datetime.fromtimestamp ( unixepochtime)

The date I get is 30 days and approximately 18 hours into the future.

I am sure that I am doing something wrong. Something obvious but I fail to see it.

Any ideas?

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Question by:geldfeld
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LVL 17

Expert Comment

ID: 34223661
Does this help?

I do not have time stamp values to test.
I also don't know whether the start date iin above link is really fine.

If you had two time stamp values with a know time distance and you know what the times should be
one could reconstruct the formula.
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LVL 2

Accepted Solution

markoilic earned 2000 total points
ID: 34223798
Hi,

try this;

datetime.datetime(1601, 1, 1) + datetime.timedelta(microseconds=last_visit_time)
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Author Closing Comment

ID: 34224185
Worked beautifully.  I tested it on pages I had browsed waking up this morning.

>>> datetime.datetime(1601,1,1) + datetime.timedelta (microseconds=12935395536392785)
datetime.datetime(2010, 11, 28, 5, 25, 36, 392785)
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Author Comment

ID: 34224193
@gelonida:

Thanks for the response.
That was my initial approach; after I reconstructed the formula incorrectly is how I got into this mess
.
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LVL 64

Expert Comment

ID: 34224249
This link should simplify the computation as it applies quite similarly for Chrome but with some tweaks, note two points
a) there is a time zone parameter factored in the code, can remove it since your formatting already factor in the locale time
b) need some 'cleaning' on the "last_visit_time" param from the "urls" sqlite table before using in the formula

Note that Chrome is not consistent with which datetime format it uses, some tables (like Firefox) use standard Unix Epoch time (microseconds since 1st January 1970) whilst in others (like Chrome) it uses its own variation of Windows Filetime (100 nanosecond intervals since 1st January, 1601 UTC) but divided by 10 to give the number of microseconds.

These sites are good references if interested
@ http://www.epochconverter.com/
@ http://docs.python.org/library/time.html
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