is_multi_author() – Checks if more than one author has published posts on the website. True is returned if two or more people have published posts. If only one author has published posts, or if no posts have been published at all, false is returned.
There are six time based conditional tags that you will also find useful. These tags refer to date archive pages. For example, the URL http://www.yourwebsite.com/2013/12/ is a month based archive page.
If any of the following conditional tags returns true, is_archive() would also be true.
is_date() – Checks if it is a date based archive page.
is_year() – Checks if it is a year based archive page.
is_month() – Checks if it is a month based archive page.
is_day() – Checks if it is a day based archive page.
is_time() – Checks if it is a time based archive page.
is_new_day() – Checks if today is a new day. If the current post was published on a different day from the previous post that was published, it would return true. False will be returned if both posts were published on the same day.