Some of the issues:
- a week is not part of a month, weeks can be in multiple months
- a week is not part of a year, weeks can be in multiple years
- months in different calendars with the same name need to be separated when they are not the same
- there are multiple divisions of a year, think months, seasons
- calendars in use in India are complex
Adding items for months that Wikipedia merged together is obvious; it is the only way to ensure consistency and add statements specific to a calendar. This may prevent the use of info-boxes for now. Such issues will arise in other places as well and there will be a solution in time.
It will help when people with expertise get involved in getting the information right.