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Asked: 2026-05-11T19:04:26+00:00

I have a UTC date time without the formatting stored in a uint64, ie:

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I have a UTC date time without the formatting stored in a uint64, ie: 20090520145024798
I need to get the hours, minutes, seconds and milliseconds out of this time. I can do this very easily by converting it to a string and using substring. However, this code needs to be very fast so I would like to avoid string manipulations. Is there faster way, perhaps using bit manipulation to do this? Oh by the way this needs to be done in C++ on Linux.

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1 Answer

  1. Editorial Team
    uint64 u = 20090520145024798;
unsigned long w = u % 1000000000;
unsigned millisec = w % 1000;
w /= 1000;
unsigned sec = w % 100;
w /= 100;
unsigned min = w % 100;
unsigned hour = w / 100;
unsigned long v = w / 1000000000;
unsigned day = v % 100;
v /= 100;
unsigned month = v % 100;
unsigned year = v / 100;

    The reason why this solution switches from uint64 u to unsigned long w (and v) in the middle is that the YYYYMMDD and HHMMSSIII fit to 32 bits, and 32-bit division is faster than 64-bit division on some systems.

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