PhoneTime is a freeware Java MIDlet for mobile phones that tells you when it is ok to call your relatives and friends living all around the world in different timezones, and when better not to call because it is night there.
For download see below.
Because of very modest requirements (it only requires MIDP 1.0/CLDC 1.0) it should run on practically any Java-enabled mobile phone that has about 20 kB free memory to store the MIDlet.
Basically PhoneTime is one of the many "world clock" programs for Java-enabled phones, albeit one of the more flexible ones: It can show as many clocks simultaneously as the screen size of your phone allows and it remembers their labels and timezones.
A speciality however is the following: In the options you can configure what are acceptable hours to call. If a local time is outside these hours the label in the clock display turns from green to red to warn you.
To keep the MIDlet simple it nows nothing about real timezones or even daylight savings time acrobatics. You must tell it how many hours the local time of the clock that you want to display differs from the hour of the internal clock of your phone, e.g. "3 hours ahead" or "6 hours behind". People who want to deal with those "strange" half-hour timezones are out of luck so far.
If you do not know the correct hour differences for the places you need there are a lot of good sites on the Internet to look it up, e.g. The World Clock.
If you have a way to transfer MIDlets from your PC to your mobile phone (which is possible for most "smartphones" like e.g. Sony Ericsson P800/P900 or the Nokia Communicator) you can download the "jad" and the "jar" file with the links below and install the MIDlet on the phone afterwards:
Download PhoneTime10.jad
Download PhoneTime10.jar (20 kB)
If you can only install Java MIDlets "over the air" (OTA) on your phone, point the WAP browser on your phone to the following litte WML page which has a link to the "jad" file:
http://dreamshare.ch/dl/
After you select that link the phone fetches the "jar" which contains the MIDlet and installs it. Please note: The program is freeware and does not cost anything, but you will almost certainly have to pay your network operator for the download.