Constraints or flexibility?

Google Calendar and Yahoo! Calendar use very different mechanisms for the "quick entry" of events.

Yahoo uses separate fields for each component of the event:

Google on the other hand uses a single text field:

Both approaches have advantages and disadvantages.

The Yahoo approach—using separate, specified fields—is probably more suitable to novice users because it ensures entries are in exactly the right format. But, it is likely slower than entering information as a single text string.

The Google approach reflects how people might quickly jot down events in an off-line context. But this also requires more system logic to properly interpret user’s entries—and this approach runs the risk that users may not use  syntax that the system can interpret, resulting in errors.

For example, consider this quick entry in Google Calendar:

breakfast w/Tracy at 7

With this entry, Google incorrectly schedules the breakfast with Tracy 7:00 pm rather than 7:00 in the morning (which was the user’s intention).