The main difference between these themes is how compact, or not their time and date format is. They each display:

• Time, and in the case of hfulldate and hornix, the date.
• Directory, with ~ being used to denote the present user's home directory.
• Operating system. If the OS is Linux (my usual OS), the specific distribution is mentioned. Colour is adjusted according to OS.
• User name. If the user is root the colour of the user name is red, otherwise green.
• Prompt icon, $ if regular user and # if root user.

hcompact uses the most time/date brief format, which merely consists of the time in 24 hour format:

hfulldate uses the most verbose time/date format, which consists of time in AM/PM format, along with day of the week in full (e.g. Monday vs Mon), day of the month, month name in full (e.g. September instead of Sep) and year name in full (2018 as opposed to 18):

hornix uses a time/date format intermediate in length: