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firstDay 1.3

The day that each week begins.

Integer, default: 0 (Sunday)

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).

In versions 1.1 through 1.2.1, this option was known as weekStart.