Hi, i trying to create a a press release page using the repeater field as per the screen shot.

In the repeater field, i will like to use the date picker function to choose. Anyone can advise how do i group the press release together via month?
Im a beginner in php, any help will be deeply appreciated. Thanks!

My advice would be to not use a repeater field for this. A better solution would be to create a custom post type for your press release section https://codex.wordpress.org/Function_Reference/register_post_type. This would also allow you to create a custom taxonomy in order to categorize your posts if you wanted https://codex.wordpress.org/Function_Reference/register_taxonomy. While adding custom rewrite rules and other code you could also create date archives for your custom post type, with a little work or could even be done using a plugin https://wordpress.org/plugins/custom-post-type-date-archives/
If you really want to use a repeater for this I would suggest looking at this turorial https://www.advancedcustomfields.com/resources/how-to-sorting-a-repeater-field/. Creating date archives for a repeater field is going to be complicated. I would suggest starting with the Dynamic $_GET parameters section of this page https://www.advancedcustomfields.com/resources/query-posts-custom-fields/
Thanks so much for pointing out the resources to look at!