System time

Library subroutines that handle such conversions may also deal with adjustments for time zones, daylight saving time (DST), leap seconds, and the user's locale settings.

Many implementations that currently store system times as 32-bit integer values will suffer from the impending Year 2038 problem.

This will also be a potentially much larger problem for existing data file formats that contain system timestamps stored as 32-bit values.

Add-on peripheral boards that included real-time clock chips with on-board battery back-up were available for the IBM PC and XT, but the IBM AT was the first widely available PC that came equipped with date/time hardware built into the motherboard.

With current technology, most modern computers keep track of local civil time, as do many other household and personal devices such as VCRs, DVRs, cable TV receivers, PDAs, pagers, cell phones, fax machines, telephone answering machines, cameras, camcorders, central air conditioners, and microwave ovens.

This routine typically adds one tick to the system clock (a simple counter) and handles other periodic housekeeping tasks (preemption, etc.)

For example, a system might return the current time as a value measured in microseconds, but actually be capable of discerning individual clock ticks with a frequency of only 100 Hz (10 ms).