Man, sometimes the simplest things in life give you the biggest headache. You’d think calculating how many days have passed since a specific date—like March 26th—would be dead simple in a spreadsheet. It’s math, right? But if you’ve been wrestling with Excel or Google Sheets, you know it can drive you nuts trying to figure out the exact formula that just works without throwing a million errors or giving you some crazy number.
I ran into this wall a few weeks back. I was setting up a dashboard for a personal side project, tracking the progress since the project officially kicked off on a random day in March. I needed a counter that automatically updated every single morning, showing exactly how many days we had logged. I started, like most people, by just trying to type the date in one cell and subtracting it from today’s date in another. Big mistake.
The Initial Mess: Why My Brain Said “Just Subtract Them”
My first attempt was pathetic. I typed “3/26/2024” into cell A1. Then, in cell B1, I tried to calculate the difference. I knew I needed today’s date, so I tried a simple function first, something like =TODAY(). That worked fine. It gave me the current date. But when I tried =B1 - A1 (or what I thought was B1 minus A1), I got either a date value that made zero sense, or sometimes just a bunch of hash signs (######) screaming that something was wrong with the number format.
It was frustrating because I knew the logic was sound: Current Date minus Past Date equals Days Elapsed. But spreadsheets are weird; they don’t see dates as dates initially; they see them as numbers, and if the formatting is screwed up, the math fails.
I wasted a good half-hour going down a few rabbit holes:
- Trying DATEDIF: This function is supposed to be the master date calculator, but it’s overly complicated if you just want simple day counts. I kept getting errors about the order of the dates, or mixing up the “Y,” “M,” and “D” arguments. Too complex for a simple task.
- Forgetting TODAY(): I tried to hardcode the date in the second cell, like
= "5/1/2024" - A1. Spreadsheets hate strings being treated as numbers, so that was a guaranteed fail. - The Formatting Dance: I kept switching the result cell (B1) between “General,” “Number,” and “Date” format, thinking maybe Excel was just displaying the right number wrong. Nope. The underlying calculation was still broken because the input date wasn’t registered correctly, or I was just confusing the software.
The Simple Realization: Dates are Just Big Numbers
I finally stopped banging my head against the wall and remembered the core concept of how spreadsheets handle time: every date is just a count of days since January 1, 1900. Once I switched my thinking, the path became crystal clear. I don’t need fancy functions; I just need to make sure the software knows what two numbers I want to subtract.
The key to making this work reliably, whether you’re using a full-blown Excel desktop application or running light in Google Sheets, is to use the dedicated functions to establish the inputs correctly.
The Right Formula: Set It and Forget It
Here is exactly how I set it up, step-by-step, to finally get that daily count ticking away perfectly:
Step 1: Setting the Start Date (The Constant)
I decided to put the start date in a dedicated cell so I could change it easily if needed. Let’s stick with our example:
In Cell A1: I entered the start date.
3/26/2024
Crucial Check: Make sure the format for A1 is indeed set to “Date.” If you type it in usually, the sheet handles it, but always double-check. A properly formatted date is now just a single number (e.g., 45376, if today is late March 2024).
Step 2: Defining Today (The Variable)
I needed a simple function that automatically pulled the current day, every single time the sheet opened or refreshed. This is where the TODAY() function comes in. It requires no inputs, which is beautiful.
In Cell B1: I entered the function for the current date.
=TODAY()
If B1 displays today’s date, great. If it displays a huge number (like 45400 something), don’t panic! That just means the format is set to “General” or “Number.” Change B1’s format to “Date.” It’s still the right number; it’s just showing it differently.
Step 3: The Simple Subtraction (The Magic)
Now that both A1 and B1 are correctly registered as simple date numbers, the final calculation is straightforward. You subtract the smaller number (the past date) from the larger number (today’s date).
In Cell C1: I entered the final formula.
=B1 - A1
Or, if you are lazy and want to do it all in one cell (and avoid using B1):
In Cell C1:
=TODAY() - A1
The Final Format Check: When you hit enter, C1 will probably try to display the result as a date again. It might show “1/31/1900” or something ridiculous. You need to tell the spreadsheet that C1 is a count, not a date.
Action: Set the format for Cell C1 to “General” or “Number.”
Boom. Done. C1 instantly showed me the exact number of days that had passed since March 26th. The best part? I checked it the next morning, and the number had automatically incremented by one. No more manual updates, no more complicated formulas that break if you breathe on them wrong.
It’s a powerful lesson, right? When dealing with complex software like spreadsheets, often the answer isn’t the obscure, fancy function you read about online. It’s usually just forcing the software to accept the simplest underlying logic—in this case, treating dates as sequential numbers—and making sure your inputs are clean. If you need a reliable, auto-updating day count, =TODAY() - [Your Start Date Cell] is the formula you need. Everything else is just noise.
