New interpretation of relative dates specified by +/-xw, +/-xM and +/-xy

Current Situation

relative dates for a "from" and a "to" date can be specified with

• ±xw (for ±x weeks)
• ±xM (for ±x months)
• ±xy (for ±x years)

to filter the data of order history, task history, auditlog and daily plan.
Here, the specification are interpreted as follows:

• ±xw is the same like ±x * 7 days
• ±xM change the month but not the day
• ±xy change the year but not the day and month

Desired Behavior

New interpretation of the above specification of relative dates in the following manner.
For the "from" date:

• ±xw -> begins always on Monday
  • Example
    ±0w -> Monday of the current week
    -3w -> Monday three weeks ago
• ±xM -> begins always on the first day of a month
  • Example
    ±0M -> first day of the current month
    -3M -> first day of the month three months ago
• ±xy -> begins always on the first day of a year
  • Example
    ±0y -> first day of the current year
    -3y -> first day of the year three years ago

For the "to" date:

• ±xw -> ends always on Sunday
  • Example
    ±0w -> Sunday of the current week
    -3w -> Sunday three weeks ago
• ±xM -> ends always on the last day of a month
  • Example
    ±0M -> last day of the current month
    -3M -> last day of the month three months ago
• ±xy -> ends always on the last day of a year
  • Example
    ±0y -> last day of the current year
    -3y -> last day of the year three years ago

Example (first quarter of the current year)

• "dateFrom":"±0y", "dateTo":"±0y-9M"

Example (second quarter of the current year)

• "dateFrom":"±0y+3M", "dateTo":"±0y-6M"

Example (third quarter of the current year)

• "dateFrom":"±0y+6M", "dateTo":"±0y-3M"

Example (fourth quarter of the current year)

• "dateFrom":"±0y+9M", "dateTo":"±0y"