Remind: The Ultimate Personal Calendar

So far, any commercial calendar package can keep up with Remind, but now we start pulling ahead of the pack.

One of the most annoying things about most calendar programs is how they handle holidays. Suppose you have a meeting every Thursday, but not if it's a holiday. The typical calendar program will go ahead and remind you anyway. Here in Canada, July 1 is a holiday and July 1, 1999, is a Thursday. Look at this script snippet:

OMIT 1 July MSG Canada Day.
REM Thursday SKIP MSG Meeting.

The OMIT line tells Remind that 1 July is a holiday, and it also prints a nice message on that date. The SKIP token in the REM line tells Remind to skip the reminder if it falls on a holiday. The reminder will thus be triggered on 24 June 1999 and 8 July 1999, but not 1 July 1999.

There are other flavours:

REM Thursday BEFORE MSG Meeting moved to preceding\
   Wednesday if Thursday is a holiday.
REM Thursday AFTER MSG Meeting moved to next\
   Friday if Thursday is a holiday.

Remind has fairly sophisticated mechanisms for adjusting reminders because of holidays and weekends; please read the manual for more information.

Figure 1. Main TK Remind Window

At this point, your head may be spinning. You don't want to learn yet another command language or obscure configuration-file format. You pine for the GUIs your Microsoft colleagues use. No problem; Remind comes with a graphical front end called TkRemind, written in Tcl/Tk. TkRemind presents a graphical calendar and lets you enter reminders with a simple graphical entry box. Figure 1 shows the main TkRemind window, and Figure 2 shows the reminder entry box.

Figure 2. Reminder Entry Box

With TkRemind, you never have to learn Remind's scripting language, as long as you can express all the reminders you need with the GUI. However, you are encouraged to learn to script Remind; from the GUI, just click “Preview Reminder” to see the Remind code which will implement your reminder.

The GUI also hinted at the existence of something called a “timed reminder”. This is a reminder with a time of day specified. You can arrange to have Remind pop up reminders just before an important meeting, or more importantly, remind you to go home.

Here's an example of a timed reminder:

REM Mon Tue Wed Thu Fri AT 17:00 +15 *3 MSG Go home!

The AT keyword introduces an “AT clause”. The 17:00 means that the trigger time is 5:00 PM. The +15 means Remind starts carping at you fifteen minutes ahead of time, and the *3 means it annoys you every three minutes.

The TkRemind front end runs Remind in a special “daemon mode” so that timed reminders like the previous example are popped up in X windows.

While what we've seen so far is quite cool, there is still the stubborn oddball reminder which requires a much tougher piece of scripting to handle. Consider the 4th of July in the U.S. If this falls on a Saturday, the previous Friday is a holiday. If it falls on a Sunday, the next Monday is a holiday. Otherwise, the 4th itself is the holiday. I won't even attempt to explain this bit of scripting; get yourself the manual, and become a hard-core Remind programmer.

Listing 1 illustrates several features of Remind scripting: Remind has built-in functions (66 of them, to be precise) and allows user-defined functions (e.g., FSET). It also has conditional tests (e.g., IF/ENDIF). A bit of clever scripting can express reminders which prove too tough for most calendar programs.

Ultimately, all calendars are derived from astronomical observations. Remind includes routines to calculate sunrise and sunset times for where you live, as well as moon phases. The moon phases were illustrated in the GUI calendar. These astronomical calculations are available as built-in Remind functions.