Week fields store a year and week number.

For historical reasons, ActivityInfo uses the epidemiological week calendar, or “epi week” used to report healthcare statistics, rather than the ISO week date system.

Week numbering

An epidemiological week, commonly referred to as an epi week, is a standardized method of counting weeks to allow for the comparison of data year after year.

The epiweek begins on Sunday and ends on Saturday. The first epidemiological week of the year ends on the first Saturday of January, provided that it falls at least four or more days into the month. Therefore, the first epidemiological week may actually begin in December of the previous year.

The WHO and national health authorities regularly publish epi week calendars for reference.

Week format

When entering a week as a text, ActivityInfo uses the format “YYYYW00”, for example “2023W1” or “2020W30”.

Data entry

Desktop data entry

Weeks can be entered either by typing the year and week number in the format “2023W51”, or by selecting a data from the calendar. When selecting a date, the data entry field will be updated with the correpsoding year and week number.


When importing, week fields should be formatted as “YYYYW00”


Weeks must be between the year 1000 CE and the year 9999 CE.


The YEAR function can be use to find the year part of the week field.

The MONTH function can be used to find the month of the first day of the week selected in a week field.

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