WEEKNUM() : week number (week starting Sunday)

The WEEKNUM function returns the week number of a given date, as a number (1, 2, 3, ...). The week starts on Sunday, and week 1 is the one that contains January 1st.

The output format of the result can be configured in the output field options of the formula editor. For more details, see Output format options in the Formula column article.

Syntax

WEEKNUM(date)

Calling function parameters in TimeTonic:

$field_name = field (link, linked table column, number, selection, formula, text...).
"free text" = free text to add between quotation marks.
Do not use quotation marks for numbers.

Parameters

# Parameter Description

1 date Date for which to calculate the week number.

WEEKNUM() or ISO_WEEKNUM()?

Function	Start of week	Definition of week 1
WEEKNUM(date)	Sunday	Week containing January 1st
ISO_WEEKNUM(date)	Monday	Week containing the first Thursday of the year

The choice between WEEKNUM() and ISO_WEEKNUM() depends on the business context (internal planning, ISO standards, delivery rounds, reporting).

Examples

Find the week number of a date

WEEKNUM(2026-1-10)

Result: 2. January 10, 2026 falls in the 2nd week of the year according to this calculation method.

Go further

ISO_WEEKNUM

The week number according to the ISO calendar: week starting Monday.

Read more →

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