Why does the default time range on the 'recent activity' page work as it does?

Question

I just went to my 'Recent Activity' page on StackOverflow and the time range offered to me by default was:

2009-10-28 13:38:20Z to 2009-10-28 23:59:59Z

Top 5 Posts
(nothing in this date range)
Most Recent Responses
(nothing in this date range)

all times are in UTC; the current time is 2009-10-28 14:00:17Z

What is the logic that generates the range shown?

It means that I am being shown less than 20 minutes of activity plus about 8 hours of future time, which might be useful to Jon Skeet, but isn't to me (I don't often get significant voting activity in just the last 20 minutes) -- I always have to go and select 'Today' to get anything meaningful.

Can't you modify the code so that the range is more like one of these:

• 2009-10-28 00:00:00Z to 2009-10-28 23:59:59Z
• 2009-10-27 14:00:17Z to 2009-10-28 14:00:17Z

(In case it is not clear - the first alternative is 'the current 24 hours aligned to the day's ends in Zulu time', and the second is 'the last 24 hours as of the current time'; the first is the range provided when you do click 'Today'.)

Answer 1

See this answer for an explanation:

Clicking envelope beside username shows fewer recent activities than “today” button

The "startdate" by default is the time current time minus the time shown in the "Last activity" line of your profile.

Frankly, I wish the default were the values you get from clicking "Today".

Alternatively, upvote my feature request here, because it's a functionality that would satisfy your needs as well:

Could we have static date range links on the Recent Activity page?