Basics

Drag Files, Mails, URLs and Contacts to the status menu in order to schedule an alarm.
For creating a manual entry - double click in the time line and start typing.

Alarms

Once an alarm occurs the status menu starts flashing.
This will continue until To shift all Alarms in the timeline at once, drag with the mouse on the hours scale

Timers

Click on the status menu hold the mouse and drag downwards to set the time of a timer.
If you change mind while dragging, drag to the left or the right

Keyboard short cuts

⇠ or ⇢ shift the time line
⇡ or ␛ close
⇧ zoom timeline to show full day
⌘-Z Undo
⌘-T show today
⌘-F Find
⌘-, Preferences
⌘-Q Quit

Third Party Software

Alarms plays well with applications that are able to sync iCal To Dos such as Things and Appigo Todo™

FAQ

Why does my Google Calendar not show up in the list?
Because Google calendars do not support To Dos.

It does not seem to sync my iCal Events, why?
It syncs To Dos (the list on the right in iCal).