From: Simon Marlow [mailto:simonmar@microsoft.com]

I think I don't really understand the (days,ticks) representation. Could somebody explain the meaning of arithmetic on this type?

Is the ticks field supposed to be limited to a day's worth? Or a day + a leap second?

I'm assuming that it's UTC (i.e. ticks = day plus optional leap second), although others might think differently...

Can I add ticks to a time? If so, don't you need leap second info to do the normalisation? Or, if normalisation doesn't happen, you need leap second info to convert to UTC, right? The only conclusion seems to be that either you can't add ticks to a time, or you need leap second info which is what we're trying to avoid.

Isn't this a general problem, rather than a specific representation problem? The only representation where you wouldn't have to know about leap seconds would be TAI. E.g. there was a leap second on 1997-06-30 23:59:60 UTC, so: - Q: how many seconds are there between 1997-06-30 00:00:00 UTC and 1997-07-01 00:00:00 UTC ? A: 86401 - Q: how many days are there between 1997-06-30 00:00:00 UTC and 1997-07-01 00:00:00 UTC ? A: 1 - Q: how long is the period between 1997-06-30 00:00:00 UTC and 1997-07-01 00:00:00 UTC ? A: 1 day 1 second, or 1 day ? (I guess just 1 day, as a day can be 86401 seconds long.) - Q: how many seconds in a day? A: 86400 (or maybe this is undefined, as it could be 86399, 86400, 86401?) - Q: what is 1997-06-30 00:00:00 UTC plus one day? A: 1997-07-01 00:00:00 UTC - Q: what is 1997-06-30 00:00:00 UTC plus 86400 seconds? A: 1997-06-30 23:59:60 UTC It gets hairy when you start thinking about durations, and I would like to see duration arithmetic in the library. I don't have any good ideas about how to handle this. Alistair. ----------------------------------------- ***************************************************************** Confidentiality Note: The information contained in this message, and any attachments, may contain confidential and/or privileged material. It is intended solely for the person(s) or entity to which it is addressed. Any review, retransmission, dissemination, or taking of any action in reliance upon this information by persons or entities other than the intended recipient(s) is prohibited. If you received this in error, please contact the sender and delete the material from any computer. *****************************************************************