Shopify loads our script asynchronously, i.e. first the page is loaded properly and then our script. So sometimes there might be an inevitable delay in loading the calendar

However, there is a workaround to load the script early along with your page. Basically, you will have to add the script directly in the head section of your theme.

To do this, please paste the following script inside the head section of your theme.

  1. Go to Settings –> Speed up Delivery Date
  2. Copy the snippet code available
  3. Go to Online Store → Edit Code
  4. Search for theme.liquid file and <head> section
  5. Paste the following snippet in the head section of the theme.
  6. Save

Here is a quick tutorial about it –