How do you subtract two dates and times from each other?

[JimT1959]

Hi Everyone,

Can anyone suggest an approach on how to subtract one time and date from another later time and date? I have an RTC that gives me the current year, month, day, hour, min and sec. I want to find the delta in seconds between this current time and an earlier time and date. Leap years are also a consideration. I looked at using look up tables for months, etc, but it got messy. I don't need the code, just the best way to handle this. I have plenty of ROM and a good amount of RAM so that will not be an issue.

Thanks!
_________________
Jim T.

[asmboy]

BTDTGTTS
one way:

1- convert the dates to seconds as 32bit unsigned int
( taking in to account leap years etc)

2- subtract lesser from greater

thats the diff in time

need more accuracy ? use msecs

[PCM programmer]

Here is a previous thread on the topic:
http://www.ccsinfo.com/forum/viewtopic.php?t=43113