InDesign template for Day Planner

Use a script

This fast one (5 minutes) inserts all dates for the coming year. Jan 1st is a friday, hence it starts with 'weekday = 5'.

var months = [ "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" ];
var length = [ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 ];
var days = [ "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" ];
count = 0;
day = 0;
month = 0;
weekday = 5;
str = "";
while (count < 365)
{
 count++;
 str += days[weekday]+", "+(day+1)+" "+months[month]+"\r";
 day++;
 if (day >= length[month])
 {
  day = 0;
  month++;
  if (month > 11)
   month = 0;
 }
 weekday = (weekday+1) % 7;
}
app.selection[0].contents = str;

Copy, paste into a plain text editor (InDesign's own ESTK is good) and save as "writeWeekdays.jsx" in your Scripts folder. Create a new text frame, have it selected, then double-click the script.