I haven't yet found a tool out there that works for me (and my probably bizarre requirements).
My solution for the time being is a spreadsheet, that maps out the entire year in months and days, including the state of the two moons. I simply type the year in question and I get the dates, days and moon phases (I have a leap year).
The moon phases are important for a number of reasons, among others, people see them as omens.
Admittedly, it requires some spreadsheet knowledge, but not that much.
I have a map and I have decided what types of climates the various areas of the map have (temperate/inland, temperate/coast, tropical, etc).
With these two things I can make the seasons and the dates quite consistent. The maps (a large one and a detailed one) are divided into 60 km and 5 km hexes resp. so the players can easily see how far they can travel by road in a day.
And yes, kilometers - none of that imperial confusion here. :-)
The various holy days, celebrations etc. that happens regularly, I simply put into RW, under The Church (so far they are all religious) in Groups. I have made a sub-group called Sacred Days.
Since we haven't run a full year circle yet, I am simply adding things here as we go forward.
Apart from that, I looked at
- Aeon Timeline
- yEd Graph editor
The Aeon Timeline might be useful for timekeeping.