doc: calendar & base date information added to time_manager_mod

[hkershaw-brown]

Description:

Added available calendar & base date information for each calendar to time_manager_mod documentation.

Added search terms for time manager (see #835) so "time manager" and "time manager mod" searches give time_manager_mod page as a result.

Fixes issue

fixes #826

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

Documentation changes needed?

• My change requires a change to the documentation.
  • I have updated the documentation accordingly.

Tests

Please describe any tests you ran to verify your changes.
Local documentation build, searched for "time manager"

Checklist for merging

• Updated changelog entry
• Documentation updated
• Update conf.py

Checklist for release

• Merge into main
• Create release from the main branch with appropriate tag
• Delete feature-branch

Testing Datasets

• Dataset needed for testing available upon request
• Dataset download instructions included
• No dataset needed

[hkershaw-brown]

Note the base dates were collected from running the code:

time = set_time(0, 0)
call get_date(time, year, month, day, hour, minute, second)