user expectation - Annual repeat on leap day

If you set an alarm to repeat annually starting on 2/29/16, would you expect the next instance on 2/28/17, 3/1/17, or 2/29/20?

Answer

Design for the user's likely intent

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  It's overwhelmingly likely that the user who indicates Annually wants the alarm to repeat annually. Allowing the leap-year technicality to prevent the alarm from going off annually is a violation of likely user intent.

  
  


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  The question then becomes, how to deal with the leap year? There are three possibilities:

  
  
  
  
  
  1. Prevent the user from selecting February 29th, since that date doesn't exist in non leap years.
  
  
  2. Snap to February 28th for subsequent years, and 29th (or 28th) for subsequent leap years.
  
  
  3. Snap to the next day (March 1st), as per #2.
  
  
  
  


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  It's more likely that users will want "annually" to mean every year, so #1 is not a great option. #3 is also not great visually since it involves snapping to another month. So #2 is the remaining reasonable option.

  
  


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  Now, you will need to inform the user since the date will be different in subsequent years. Since you're on Android, a good way to do this is to use a toast which can pop up to inform that user:

  
  
  
  
  
  • This annual alarm will go off on February 28th when it isn't a leap year.