In the modern world, timekeepers can show time, date and weekday.
So decide how much space you want for your writing. This will make it so much easier to find the right journal for the job. This applies for the Julian day or Unix Time.
Consecutive days may be grouped into other periods such as the week. Please help to ensure that disputed statements are reliably sourced.
Because the number of days in the tropical year is not a whole number, a solar calendar must have a different number of days in different years.
Also a calendar may, by identifying a day, provide other useful information about the day such as its season.