Instructions for an example of a public transport ticket for changing trams, buses and overhead trains with a limited period of validity.
“Pattern of a transfer ticket for the tram, bus and elevated rail traffic, the validity of which is limited to a certain time."

three white days: Monday, Wednesday, Friday
three green days: Tuesday, Thursday, Saturday
The concentric circular rings mean the days of the week
a red day: Sunday
"The conductor clicks in the clock in the ring of the relevant weekday the time of boarding, which can be displayed for at least 10 minutes exactly. [...]
the thinner radii lying between the hour radii denote the 10. 20. 30. 40. u. 50th minute of boarding. The conductor marks here with a clippers weekday and hour.”
Maybe this is why we have monthly transport passes...