(PHP 4, PHP 5, PHP 7, PHP 8)
jddayofweek — Returns the day of the week
Returns the day of the week. Can return a string or an integer depending on the mode.
julian_dayA julian day number as integer
mode| 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) |
The gregorian weekday as either an integer or string.
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.