date.txt (date period)
Contains one data record for each week for which the timetable data are available.
1 char - calendar week, e.g. 38
2 char - day and month of the Monday in this week, e.g. 18.9.
3 date - full date of the month in the form YYYYMMDD e.g. 20170918
4 char - school week, e.g. 1
38 18.9. 20170918 1