convert string format to timestamp

[turalmirza]

{
"id": 329,
"username": "demo",
"last_activity_on": "2024-06-29"
}
hi , I have a json output like this.i use last_activity as label in my metrics. but in promtheus side when i want to list last_activiy users more than 30 day promtheus cant understant it. beacuse date format writing in label as a string format. how can i solve this problem?
here is my config file

modules:
gitlab:
metrics:
- name: user_info
type: object
help: "User ID fetched from JSON"
path: '{ [*] }'
labels:
username: '{.name}'
last_activity: '{.last_activity_on}'
values:
user_id: '{.id}'
http_client_config:
tls_config:
insecure_skip_verify: true