Adam Erstelle

This plugin allows a wordpress administrator to schedule a different theme to display on the website for holidays or special events for all visitors.
The theme will be overridden on the live site for all people who visit the site. Great for setting a Christmas theme!
If you just want to have a css file added instead of a whole theme, check out the wp-scheduled-styles plugin.

WP Scheduled Themes

Schedule a theme to display on the live site for holidays or special events. (Available from Appearance - Scheduled Themes)

nxtweb

Next Tiny Date allows you to propose an appointment booking form on your website through the adding of a simple shortcode. 
Configure your opening hours, add your reasons for appointment. 
Set the bank holidays and configure the dates of your holidays. 
Choose the appointment duration. 
Then let clients book directly in a week view from your website! 
You can then view your appointments or cancel them. 
Lock or unlock some appointment slots for personal use, export them in a .CSV file… 
It can send confirmation emails, and redirect to a payment page. 
It generates stats with pie and bar charts of number of appointments per day and per reason of appointment. 
Usefull for health professional for medical appointments, teachers with different types of courses, business people for planing meetings… 
Very light and easy to use!
<h3>Languages</h3>
This plugin is available in English & French.
<h4>Custom development</h4>
You need a new plugin? We can talk and help you with the plugin custom. 
Just contact us on: https://nxt-web.com/

Next Tiny Date

Next Tiny Date allows you to propose an appointment booking form on your website through the adding of a simple shortcode.

WP Scheduled Themes vs Next Tiny Date