ColorCal
Color and Alpha (A-F) Coded calendar for Carriers and Clerks using USPS Sunday/Rotating Scheduled Day Off (SDO) calendar
This calendar spans October 2019 (USPS 2020 Q1 ) thru January 2021 (USPS 2021 Q1)
NOTE: The SDO scheme depicted in this calendar, matches commonly available printed calendars. Your office may vary. I also have single color calendars is that is an issue for you

Check out the single color version of ColorCal for note keeping ability
For security, there is no online calendar integration. It simply displays your scheduled day off, holidays and paydays. NO complicated or intrusive settings.
There is no SPAM, Ads, pop-ups, nag screens, push notifications, in-app purchases or collection of personal data. It does not collect, save or ask for ANY information. The app works without connectivity.
WARNING: ONLY get my app from Google PLAY OR the Amazon APP store. Other sources may provide unsafe and/or altered (hacked) apps whose safety cannot be verified.
Requires Android version 5.0 or higher.
The calendar is believed to be correct. By using it you agree to hold me harmless in the event of errors or omissions