Working time model
- indicates how many working hours a member has per week
- this can be a simple rule
   like 8-16, Mon - Fri - result: 40 h
- or several rules:
   1. Mon - Thu, 8 am - 4 pm
   2. Fri, 8 am - 14 pm
   Result: 38 h

Time Account
- Working hours are posted to this account
- At least one time account is required
- For multiple time accounts, one must be considered primary
- all other time accounts with content appear on the evaluation as a surcharge

Tariff model
- determines according to which rules the registered working hours are booked
- Only entries on the primary time account are used for the evaluation
- all other time accounts are shown as surcharges
- Time account rule
   + a rule to book a registered working time on an account
   + Rules can be active at: 
      only certain times of the day or 
      on certain days or
      24h / 7days
   + Several rules can be active at the same time, for example a late shift
     to book as normal work as well as late shift supplement
     (in this case, several times account entries are created per work time entry)

Holidays
- The holiday is entered in the holiday calendar by the employee
- The holiday calendar is the calendar set on the employee
- The cron job periodically updates the vacations in the current evaluation
- a day of vacation is counted if there is a working time on this day and:
 + it is a 'full day' and there is no presence on that day
   (planned working time = actual working time is calculated)
 + it is half a day, working hours are allowed on this day
   (half planned working time + registered working hours are calculated)
- at a half holiday the registered working time can be reduced by the break time regulation
- Number of vacation days in evaluation: the actually counted vacation days are spent (whole / half)
- Remaining days are: the current value for the number of Holidays + special leave of the employee
  from the beginning of the year or the beginning of the work and up to the current evaluation
  Holiday days are calculated
