[fvirexi]

I find this a really good argument for it: how are you supposed to know if you call somebody in the middle of the night, if it's noon where you are, and the hour is the same? By having different time-zones, you need to look it up, but then you have an intuitive way of judging which stage of the day they are perceiving.

[hrjet]

No, time-zones alone can't give you an estimate of sleep-times (even ignoring individual sleep patterns for the moment).

Time-zones are related to the longitude of the location You also need to account for the latitude, and the time of the year, because the pattern of day and night depends on all three factors.

[Expez]

You are complecting two problems: 1) When does the other person sleep. 2) What does his watch show.

Making 2) easier does not change anything with regard to 1).

[philwelch]

For most people, their sleep is highly correlated with what their watches show.

[fvirexi]

It doesn't change the sleep patterns, but would you say it does not make a difference in judging at which hours other people sleep?