# firstDay

> FullCalendar v1 documentation, for an old release. Web version: https://legacy.fullcalendar.io/v1/firstDay
>
> Latest version (v7): https://fullcalendar.io/docs/firstDay.md

The day that each week begins.

<div class='spec' markdown='1'>
Integer, *default*: `0` (Sunday)
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The value must be a number that represents the day of the week.

Sunday=`0`, Monday=`1`, Tuesday=`2`, etc.

This option is useful for UK users who need the week to start on Monday (`1`).

<div class='version-info' markdown='1'>
In versions 1.1 through 1.2.1, this option was known as *weekStart*.
</div>