Nah you have to think more like a PIC guy and less like a clock guy...
Put some buttons on the back of the unit, say one button for each clock mechanism you need to step.
Then get the PIC to auto-step the mechanisms, probably with 2 speeds so single presses of the button makes a single step, and holding the button down steps it quickly to quickly position the hands.
But I don't think you've addressed the main issue of operation... Assuming the unit updates itself properly in operation;
1. how do you set the initial calendar day month year etc as stored in the PIC eeprom?
2. how do you know that the PIC eeprom has the correct data stored at any time?
3. how do you fix the stored data if the unit experiences a fault, power outage etc?
As a worst case you could do this;
1. you program in the calendar/tide settings on the day you activate it
2. you would know if something is wrong at each month end/leap year etc if the calendar fails
3. it's never gonna fail because your Julian calendar/tide map etc was alll perfect in every way the first time you programmed it and it will never get a broken wire or power outage
These are all pretty poor solutions.
A more pro solution would be to put a little numeric display on the back of the device that with a button press would show you the hour/day/month/year etc. This would also make it easier to set the internal settings if/when they need to be changed updated etc. But that might be too complex.
Like every design there might be a clever intermediate solution.