After this refactoring:
1. Timezones parses only once on start and the we refer to saved values. All time_zone.isString() checks gone to the constructor.
2. Single timezone case handling as case of multi timezoned logic.
3. Scroll event seems more clear now.
4. Tooltip template parses on start to check if there calendar placeholder or not. To do not calculate calendar_text() if not necessary.
Also fixed timezones behavior: now waybar starting with the first timezone in timezones list and falling back to timezone field only if timezones omit or has no elements.
Sergey Mishin