There are multiple implementation of Runnable based on conf in different plugins
Runtime :

• handles daily and weekly
• hour and day are mandatory parameters

Page subscription :

• handles daily, weekly and monthly
• hour and day are optional parameters, default value are used if absent
• monthly triggers every first day based on the day configured (ex the first monday of the month)

Workspaces :

• handles daily, weekly and monthly
• hour is an optional parameter, if absent, the runnable is disabled
• weekly triggers on monday
• monthly triggers on first the of month (the 1st)

Providing a monthly implementation in Runtime and uniformizing the handling of mandatory/default value should make it possible to only have the runtime implementation.