FORMULA & SQL / DATES

First day of the month.
Tested, not guessed.

The Excel and Google Sheets formula and the SQL query, each run on the rows below. Open this with your own data ↗

The example rows

Row	A: Region	B: Rep	C: Amount	D: Order Date	E: Status	F: Customer
2	North	Ana	1,200	2026-03-01	Paid	Jo Smith
3	South	Ben	450	2026-03-15	Open	Raj Patel
4	North	Cy	300	2026-04-02	Paid	Lee Wong
5	East	Ana	980.50	2026-04-20	Paid	Mia Ross
6	North	Ben	75	2026-05-05	Open	Jo Smith
7	West	Dee	1,640	2026-05-18	Paid	Sam Okoro

Excel

=EOMONTH(D2,-1)+1

The last day of the month minus 1 months from Order Date (D2) plus 1.

Run on the example rows:

PostgreSQL

SELECT *, DATE_TRUNC('month', order_date) AS month_start
FROM sales

Run on the example rows:

region	rep	amount	order_date	status	customer	month_start
North	Ana	1200	2026-03-01	Paid	Jo Smith	2026-03-01
South	Ben	450	2026-03-15	Open	Raj Patel	2026-03-01
North	Cy	300	2026-04-02	Paid	Lee Wong	2026-04-01
East	Ana	980.5	2026-04-20	Paid	Mia Ross	2026-04-01
North	Ben	75	2026-05-05	Open	Jo Smith	2026-05-01
West	Dee	1640	2026-05-18	Paid	Sam Okoro	2026-05-01

Other databases

MySQL

SELECT *, DATE_FORMAT(order_date, '%Y-%m-01') AS month_start
FROM sales

SQL Server

SELECT *, DATEFROMPARTS(YEAR(order_date), MONTH(order_date), 1) AS month_start
FROM sales

SQLite

SELECT *, strftime('%Y-%m-01', order_date) AS month_start
FROM sales

BigQuery

SELECT *, DATE_TRUNC(order_date, MONTH) AS month_start
FROM sales

Snowflake

SELECT *, DATE_TRUNC('month', order_date) AS month_start
FROM sales

Paste your rows into the free tool and it writes this for your columns, then runs it on your data before you copy it. Open the tool ↗