Enter it in the Log.

Today, I made history - enter it in The Log; I wrote a letter. 
I have a "Foxgloveless" friend living "downcountry" a bit. I have plenty and each yields, probably, several 1,000s or even 10s of 1,000s of seeds.
I dived into what I'll humorously describe as the Stationery Store in search of an envelope; where I found this.
I haven't a clue how long I've had it, BUT I'll guess I got it round about the time I went to College, (1962). I, further, have no idea when it was last used.
Noticing the Calendar, I thought "I wonder how old it is?"
Answer - not a bleeping clue; some clever old @£$%^ had designed a perpetual calendar. 
Thus:-
Four sheets with four months to the sheet.
Four sheets each with a different weekday to start the month = 7 plus a spare side bearing explanation; though I must admit I'd sussed the system before I found the explanation.