JDDayOfWeek
(PHP 4, PHP 5)
JDDayOfWeek — Returns the day of the week
Description
Returns the day of the week. Can return a string or an integer depending on the mode.
Parameters
-
julianday -
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.
Коментарии
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.
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.