On my Aquaris 4.5, OTA-13, indicator-datetime 15.10+15.04.20160820.1-0ubuntu1, it uses too much RSS. A typical RSS is 315892, almost three times as much as unity8.
I believe this is an OTA regression. I'm not sure if it regressed from OTA-11 or OTA-12.
Just now, I got caught in an oom killer loop with constant killing of unity8-dash because of this, making my phone unusable. I had to kill indicator-datetime manually. It then restarted automatically and now uses 80456 RSS only. I see bug 1633319 exists complaining about a memory leak. It's not exactly the same version since mine is 15.10+15.04.20160820.1-0ubuntu1 and that one is 15.10+16.10.20160820.1-0ubuntu1. But perhaps the upstream versions are the same or something? Perhaps the two are dupes, but I'll let someone more familiar make that determination.
I have only a handful of alarms (perhaps five on average; rarely more) but I do have my Google calendar syncing with perhaps hundreds of events. However, there's no reason that this should cause indicator-datetime to use more RSS; it shouldn't be keeping these in memory.
Status changed to 'Confirmed' because the bug affects multiple users.