Week formats are represented as "YYYY-Www," where YYYY denotes the year, and Www is the week number. For example, the first week of 2023 is denoted as "2023-W01".

ISO format

• The week starts on Monday.
• This system is based on the ISO 8601 standard and is widely adopted internationally. In the ISO system, weeks are formatted from 1 to 52 or 53 in a year. The first week of the year is defined as the week that contains the first Thursday of the year. Therefore, if January 1st falls before Thursday within a week, it is included in the previous year's final week. Typically, January 4th is included in the first week of the year.

US format

• The week starts on Sunday.
• The United States follows a different method for calculating week formats. Here, the week containing January 1st is considered the first week of the year. Therefore, week numbers range from 1 to 52, and because January 1st is within a week, the year starts with week format 1.