Postgres-XL is a massively parallel database built on top of and very closely compatible with PostgreSQL 9.5. It is flexible enough to handle OLAP & OLTP workloads and is Horizontally Scalable with all the features of PostgreSQL.
Working with calendars can be surprisingly frustrating from various formats to dealing with the nuance of leap years. Postgres yet again can do much of the hard work for you as shown here.