I would like to know how the calculation is happening for DatedConversionRate's nextstartdate, is it depends on some configuration setting?
This value is simply whatever the next DatedExchangeRate's StartDate is.
For example, if you insert first record with a StartDate for
2020-01-01, then you insert another record for the StartDate
2021-01-01, the NextStartDate for
2020-01-01 will be set to
If you later add a record with a StartDate of
2020-06-01, then the NextStartDate for
2020-01-01 will change to
2020-06-01, and the NextStartDate on
2020-06-01 will be
This is all done by the server, so you don't need to worry about managing this.
This is a feature of Advanced Currency Management, where you can set exchange rates for a particular time period.
It includes a link to more detailed information on dated exchange rates.