# Most useful spreadsheet ever? Excel-based year calendar

I created an Excel year calendar recently. Here's a link to it. It's completely dynamic, allowing you to show the calendar for any year between 1900 and 9999. The only user interaction is to enter the year. The rest of the calendar updates automatically.

Below is the logic I used.

The first thing to do was to work out the day of the week on which 1 January fell. So I concatenated the year on to the string "01/01/" and the value from concatenated the year on to "01/01/", and calculated its weekday from there.

=VALUE("01/01/"&A1)

The ampersand is a shorthand route to accomplish the CONCATENATE function. =A1&A2 simply butts the contents of A1 up to the contents of A2. The VALUE function tries to interpret the text that results from the CONCATENATE function as a value. It sees it as a date, and so stores that date in the cell.

To calculate the day of the week of that date, I used the WEEKDAY function.

=WEEKDAY(B1,2)

This returns a serial number between 1 and 7, 1 meaning Monday, 2 Tuesday through to 7 Sunday. The "2" at the end of the formula determines how to return the weekday. I always use 2, as I always think of Monday being the first day of the week. But you could use 1 to allow your week to start on a Sunday; of 3 if you'd prefer 0–6 instead of 1–7.

Next, I created a table showing each of the months' lengths. Eleven of them hardcoded, as they're the same length every year. February’s entry used the slightly cumbersome formula for working out whether a year leaps. Years divisible by 400 are leap years; those divisible by 100 are not; those divisible by 4 are; all others are not. In that order. The formula for determining whether a year is a leap year is as follows:

=IF(MOD(A1,400)=0,"Yes",IF(MOD(A1,100)=0,"No",IF(MOD(A1,4)=0,"Yes","No")))

The results of that were used to determine whether to populate the number of days in February with a 28 or a 29.

=IF(B4="Yes",29,28)

I completed the table with the following columns: first day of the month (as a serial number again), last day of the month, and the last day of the previous month. This used similar concatenation logic to that described above—creating a date text string, interpreting this as a value and calculating its weekday.

That was all the data I needed to drive the calendar, and I put it all on a working sheet. The visual calendar was placed on a separate sheet, headed with the year that drove some of the formulae described above.

On the calendar sheet, the first row of January’s dates was created by comparing the number of the day of the week each cell represented with the day the month started on to establish whether to show a blank (the month hasn’t yet started) or a number—either a 1 for the first day, or the previous cell plus 1 for subsequent days.

The subsequent rows’ entries simply compare the previous day with the number of days in that month. If the two are equal, then that and subsequent entries display blanks; if not, then we simply increment the previous entry by one.

Each month has six rows of entries to accommodate the rare months that start late in the week and drip a day or two into week six—January 1900 being a good example, starting on a Sunday.

Once the numbers are in place, the remainder of the look and feel is accomplished through conditional formats. Blank cells have no borders; those representing weekends are shaded with borders; those representing weekdays are clear with borders.

Combining so many beautiful elements of Excel into a spreadsheet so useful was rewarding to say the least. I hope you enjoy the logic and can find a use for the calendar.

This entry was posted in Tools and tagged , , , , . Bookmark the permalink.

### 6 Responses to Most useful spreadsheet ever? Excel-based year calendar

1. Julianne says:

This is awesome! Thank you!

2. Fraser says:

I know this is an old post, but I just found it, and it was very helpful. There is a simpler way to determine if it is a leap year using the system's calendar.
=DAY(VALUE("3/1/"&Annual!A1)-1)
This will subtract one day from March 1, and return the day value (28 or 29).

3. Wroebuck says:

I was looking into developing this very thing...Thanks for sharing!

4. Laura Tarrant says:

TY TY TY!!

Now, I found you while googling for answers in excel 😀

My hickup is this:

I have a client list that I work from
I schedule out their appointments a year ahead.

I would like to know which customer is coming on which day and move them around easily. Much like making entries in a calendar, but I need to customize what information it shows.

I am not very familiar with VBA yet, dabbled at best.

I am thinking, I don't have the data set up on a sheet in the best way, for starters. It takes me AWHILE to work threw a formula, but I'm getting better at reading them, so thats improved. I have used excel for many years to get this accomplished. Just hoping one year, I won't try to improve it and it take months to get organized.

Anyway,

Looking for some ideas 😀 and Thank you, again, for this amazing workbook!! It has saved me TONS of time!!

5. Alec says:

My only problem I'm having implementing this is that the actual date each month is January. If you format your February dates into mm/dd they'll come out 01/01, 01/02, etc. Trying to find out a workaround

6. Jake says:

Note that the Match function on the array of cells containing the days of the week will return the index needed for the first row compare. This gets rid of the need for the hidden row of numbers A3:G3 in Annual.