I had the same thing after a clean install. Maybe its the same after an update. Android system consumed most power, this stopped after approx 9 days and the battery life went up. Just give it some time to do its thing in the background and the battery life will be like it was. At least that is...
Pinch homescreen -> widgets -> search glass thing top right corner -> Android widgets bottom screen. The Android widgets including calendar one is in there
I am on Mi11le Lisa, standby drain is the same. clearing Play services cache and data helps for some time. But after a while the drain will be back. Could be placebo though. Maybe battery backup on Lisa just isnt that great.