MIDlets may need to delay or schedule activities to be performed at a later time. The MIDP Specification provides two mechanisms to enable this:
Timers are used for time-based events while a MIDlet is running. For example, a timer used to change the frame being shown in an animation sequence. Timers are covered in this section.
Alarms provide a one-shot time for MIDlets to be launched if they are not already running. Automatic launching can be convenient, for example, to register the next appointment in a calendar. Alarm-based MIDlet launching is covered in Section 17.1, “Alarm-Based MIDlet Launch.”
The MIDP Specification