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Date functions

Week Functions

Get the day of the week or week number for a date. Use these functions to skip weekends in delivery estimates, group data by week, or build logic that depends on specific days.

Functions

  • WEEKDAY — Day of the week as a number

  • WEEKNUM — ISO week number (1-53)

WEEKDAY

Syntax: WEEKDAY(date, type)

Returns the day of the week as a number.

Parameters

  • date (Date or DateTime): The date to evaluate

  • type (Number, optional): Numbering system

    • 1 (default): Sunday = 1, Monday = 2, ..., Saturday = 7

    • 2: Monday = 1, Tuesday = 2, ..., Sunday = 7

Returns

Number from 1-7 representing the day of the week.

Examples

Check if it's a weekend:

WEEKDAY(CURRDATE()) = 1 OR WEEKDAY(CURRDATE()) = 7

Skip weekends in delivery estimate:

ESTIMATED_DATE = ADDDAYS(ORDER_DATE, 5)
IF(WEEKDAY(ESTIMATED_DATE) = 1, ADDDAYS(ESTIMATED_DATE, 1), 
   IF(WEEKDAY(ESTIMATED_DATE) = 7, ADDDAYS(ESTIMATED_DATE, 2), 
      ESTIMATED_DATE))

Weekend pricing:

IS_WEEKEND = WEEKDAY(EVENT_DATE) = 1 OR WEEKDAY(EVENT_DATE) = 7
IF(IS_WEEKEND, PRICE * 1.3, PRICE)

Business day check (Monday-Friday):

WEEKDAY(DATE, 2) >= 1 AND WEEKDAY(DATE, 2)

Display day name:

DAY_NUM = WEEKDAY(CURRDATE())
IF(DAY_NUM = 1, "Sunday", 
   IF(DAY_NUM = 2, "Monday", 
      IF(DAY_NUM = 3, "Tuesday", "...")))

Use type 2 (Monday = 1) when building business day logic or working with ISO standards. Use type 1 (default) for weekend checks.

Type 1 (default): Sunday = 1. Type 2: Monday = 1. Choose based on your needs.

WEEKNUM

Syntax: WEEKNUM(date, type)

Returns the ISO week number of the year (1-53).

Parameters

  • date (Date or DateTime): The date to evaluate

  • type (Number, optional): Week start day

    • 1 (default): Weeks start on Sunday

    • 2: Weeks start on Monday (ISO 8601 standard)

Returns

Number from 1-53 representing the week of the year.

Examples

Group orders by week:

WEEK_NUMBER = WEEKNUM(ORDER_DATE, 2)

Weekly report label:

`Week ${WEEKNUM(CURRDATE(), 2)} - ${YEAR(CURRDATE())}`

Check if same week:

WEEKNUM(DATE1, 2) = WEEKNUM(DATE2, 2) AND YEAR(DATE1) = YEAR(DATE2)

Week-based billing period:

BILLING_WEEK = WEEKNUM(CURRDATE(), 2)
IF(BILLING_WEEK % 2 = 0, "Billing week", "Off week")

ISO 8601 standard uses Monday as the first day of the week. Use type 2 for ISO compliance.

Some years have 53 weeks. Week 1 is the first week with 4+ days in the new year.

Common Patterns

Weekend check:

IS_WEEKEND = WEEKDAY(DATE) = 1 OR WEEKDAY(DATE) = 7
IF(IS_WEEKEND, "Closed", "Open")

Business day validation:

IS_BUSINESS_DAY = WEEKDAY(DATE, 2)

Adjust delivery for weekends:

DELIVERY = ADDDAYS(ORDER_DATE, 3)
ADJUSTED_DELIVERY = 
  IF(WEEKDAY(DELIVERY) = 1, ADDDAYS(DELIVERY, 1),      // Sunday → Monday
     IF(WEEKDAY(DELIVERY) = 7, ADDDAYS(DELIVERY, 2),   // Saturday → Monday
        DELIVERY))

Week-over-week comparison:

CURRENT_WEEK = WEEKNUM(CURRDATE(), 2)
LAST_WEEK = WEEKNUM(ADDDAYS(CURRDATE(), -7), 2)

Friday discount:

IF(WEEKDAY(CURRDATE()) = 6, PRICE * 0.9, PRICE)

Common Mistakes

  • Forgetting type parameter affects numbering: Type 1: Sunday = 1. Type 2: Monday = 1. Default is type 1.

  • Comparing weeks across years: Week 1 of 2024 ≠ Week 1 of 2025. Always check YEAR() too.

  • Assuming Week 1 = January 1: Week 1 is the first week with 4+ days in January. Jan 1 might be Week 52 of the previous year.

  • Using WEEKDAY for business days without type 2: Use type 2 (Monday = 1) for easier Monday-Friday checks.

See Also

CURRDATE · DATE · DAY · MONTH · ADDDAYS · DATEDIFF

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