Almost There
This app has been steadily improving and currently it’s the only calendar app I use across all my devices (5s, iPad mini, iMac). It is consistent, up to date and bug free from my experience in the last month (mid-July to mid-August 2015). It does lack some functionality that is annoying. Not dealbreakers, just annoying. Here are two easy improvements that could put Sunrise over the top:
1) Allow to copy and paste events. Simple in iCal, impossible here.
2) Allow custom alerts. Without the custom alerts option, it is impossible to automate an email to send later. This is a great, if little known, OSX tool that is completely lost by using Sunrise’s limited alerts menu.
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Sunrise Calendar