This microservice functionalities are:

Recurring Dates

Computing of recurring dates based on very flexible recurrence rules as defined and specified in the
iCalendar RFC 5545.

Day Count Conventions

Computing an accrual factor according to a day count convention, which represents the fraction of a year a given period. The most day count conventions are taken into account.

Here is wiki link on the description of the most used day count conventions.

Time Zones

Computing accurate and cross platform timezone based on the tz database; This Time Zone Database (often called IANA timezone database, tzdata or zoneinfo, and occasionally as the Olson database) contains code and data that represent the history of local time for many representative locations around the globe. It is updated periodically to reflect changes made by political bodies to time zone boundaries, UTC offsets, and daylight-saving rules.

Here is wiki link to aware about the complete list of tz database time zones.

Relative Date Time

Computing:

• relative date or datetime in the future or past. You can use this feature to calculate expiration dates, maturity dates, contract dates, and other due dates;
• number of years, months, days, hours, minutes, seconds or microseconds between two dates or datetimes.