Currently you cannot change the timescale for Gantt charts . This is an issue because company I work for starts their planning year in February but by default the Gantt chart will show week 1 starting in January even though the model timescale is set to start in February.
It would be great if these could align or even if we could disable the showing of weeks and just have it show months (right now it auto-zooms depending on size of screen and how large the timescale you are trying to show)