MCPblog

You have spent noumerous hours bowsing throug your PocketPC device searching for option to change "working hours" in the calendar. It there a easy way? No! You need to tweek your registry. (www.resco.net for registry)

Default value for 8am-5pm:
HKLM\Software\Microsoft\Calendar\ActiveTimes\ActiveTimes = 2210003E (DWORD hexadecimal)
For 9am-5pm:
HKLM\Software\Microsoft\Calendar\ActiveTimes\ActiveTimes = 2212003E (DWORD hexadecimal)
For 2pm-10pm:
HKLM\Software\Microsoft\Calendar\ActiveTimes\ActiveTimes = 2C1C003E (DWORD hexadecimal)

The first 2 characters define the ending hour as a count of half hours since midnight, in hexadecimal. So for midnight, it would be 0 half hours in hexadecimal = 0. 5pm is 17 hours, or 34 half hours. 34 in hexadecimal is 22. 10pm is 22 hours, or 44 half hours. 44 in hexadecimal is 2C. You can use a calculator capable of hexadecimal conversions to get the hexadecimal number.
Similarly, the next 2 characters define the starting hour as a count of half hours since midnight, in hexadecimal. So for 8am.. 16 half hours, 16 in hexadecimal is 10. 9am = 18 half hours = 12. 14h = 28hh = 1C.
Using the above, you should be able to se the working hours to whatever you'd line. Note that this value also adjusts the working DAYS. The examples here all use the default Mon-Fri workweek. See the "Change Calendar 'working days'" tweak to modify this. Note that the ActiveDays key and value may not exist. Simply create them first. Note that you cannot set the End time earlier than the Start time, for obvious reasons. Note that you cannot set a Midnight end time. The best you can do is 11.30pm (2F).
More tweeks can be found on http://www.freddyreyes.com/forums/index.php?topic=120.5;wap2