Due date generation always based on most recent date not initial date

[tmfrnz]

When adding a monthly due date schedule and the start date is set to January 31st, the subsequent due dates will be

• February 28th
• March 28th
• April 28th
  ...

The expected result would be

• February 28th
• March 31st
• April 30th
  ...

[tmfrnz]

If the start date is the last day of a month, subsequent dates should always also be the last days of the respective months