The analog of java.util.Calendar in Ionic

Question

I need to do calculations like:

• Given Unix time, tell the day of week.
• Add given number of seconds to the known date, and get the new date.
• Get the time (duration) difference between the two dates.

Ideally it should figure out for me the number of working days between the two Unix times but I understand that this may be too much.

When using Java, I would use java.util.Calendar for all these tasks. Which tools should be used in Ionic framework to get the same functionality? I tried to google "calendar ionic" but all results point to the Calendar GUI component that is not relevant for my task.