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jddayofweek

(PHP 4, PHP 5, PHP 7, PHP 8)

jddayofweek — Returns the day of the week

Description

jddayofweek(int $julian_day, int $mode = CAL_DOW_DAYNO): int|string

Returns the day of the week. Can return a string or an integer depending on the mode.

Parameters

julian_day

A julian day number as integer

mode

**Calendar week modes**
Mode	Meaning
0 (Default)	Return the day number as an int (0=Sunday, 1=Monday, etc)
1	Returns string containing the day of week (English-Gregorian)
2	Return a string containing the abbreviated day of week (English-Gregorian)

Return Values

The gregorian weekday as either an integer or string.

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User Contributed Notes 2 notes

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-2

kevind at communitycolor dot com ¶

6 years ago

You need to check to see how your client wants to represent the day of week. This function returns 0 for Sundays. ISO 8601 uses 7 for Sundays.

BTW, You can also calculate the day of week with modular division:

$dow = (1 + $julianday) % 7; // returns 0 for Sundays.
$dow = ($julianday % 7) + 1; // returns 7 for Sundays.

https://en.wikipedia.org/wiki/Julian_day#Finding_day_of_week_given_Julian_day_number

To make matters confusing. The Julian Date starts at noon UTC. Some programs such as SQLITE3 use real numbers to record date and time. If you pass this function a float; it will return a different day of week for the morning than for the afternoon.

When given a julianday with a decimal part you will need to add a half day and may need further adjustment for your timezone.

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phimuskapsi at gmail dot com ¶

3 years ago

When using mode 1 or 2, the number returned will NOT match mode 0. 

jddayofweek(0, 1) = 'Monday' not 'Sunday' as expected. 

This can cause discordance between the UI and the value saved.

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