Info
You can change basically any of the text seen in the Cowlendar calendar widget by going into Apps > Cowlendar > Settings > Translation
Steps on how to change the text in the CTA (call to action) button
In your Shopify admin dashboard look at the left panel and click on Apps.
Click on Cowlendar.
Click on Settings.
Click on Translations.
Change the Product page button label to update the text shown in the Book Now button
Info
Translation tab is where you can translate 99% of the text show in the Cowlendar calendar