Date Mastery: Using Excel Formulas to Set Up a Dynamic Monthly Calendar

A static calendar is useless next year. The power of Excel comes from creating a **dynamic calendar** that changes the entire grid just by changing one cell—the month/year input.

We'll use a few key date functions to calculate the first day of the month and then auto-populate the rest of the 42 cells (6 weeks x 7 days) that make up a standard monthly calendar view.

Step 1: Set the Input and Find the Start Date

Dedicate one cell (let’s use **A1**) for the user to input the target month and year (e.g., enter `1/1/2026`).

In a nearby cell (**B1**), we calculate the actual date of the first day that needs to be displayed in the calendar grid. This is usually a day from the *previous* month.

The Start Date Formula:

=A1 - WEEKDAY(A1, 2) + 1

How it works:

• WEEKDAY(A1, 2) returns the number of the day of the week (1=Monday, 7=Sunday) for the first day of the month.
• Subtracting this from A1 finds the Monday *before* the start of the month.
• Adding `+1` shifts it to the appropriate Sunday or Monday (depending on your layout) that starts the visible calendar week.

Step 2: Building the Grid

Now, we build the grid of 42 cells, starting with the date calculated in **B1**.

1. In the top-left cell of your calendar grid (**C4**), simply enter:

   =B1

2. In the cell immediately to the right (**D4**), enter the formula for the next day:

   =C4 + 1

3. Drag this formula across the first row (7 cells).
4. For the second row, the first cell (**C5**) should reference the last cell of the previous row (**I4**) plus one day:

   =I4 + 1

5. Drag this formula across and down to fill the entire 6-row grid.

Now, when you change the date in cell **A1**, the entire calendar grid adjusts perfectly!

Step 3: Clean Up (Show Only the Day)

To make the calendar look clean, use the **Custom Number Format** (`d` or `dd`) on all 42 grid cells to display only the day number, hiding the month and year.

Use **Conditional Formatting** to dim the dates that fall outside the current month (i.e., dates from the previous or next month) for a professional look.