Not sure if this is going to work since you are using deprecated config format (new one is yaml), but according to documentation at https://www.mediawiki.org/wiki/Manual:Huggle/Deploying/DefaultConfig.yaml

##############################################################################
# Reverting and templates
# Configuration of reverting and various templates
##############################################################################
# Specify type of headings to use when sending a message to user
# standard will use text in "template-header"
# page will use page in question as header
# none will not use any headers
headings: standard

# Use for "standard" headers. Uncomment if you want to change it # LOCALIZE ME #
# template-header: "Your edits to $1"

You can see that if you change headings to standard, then you can define which text will be used for template header. I suppose it could contains some wiki-text that would have the timestamp in format you prefer.

For example:

template-header: "{{CURRENTYEAR}}年{{CURRENTMONTH}}月:"

In T216858#5191117, @Petrb wrote:

You can see that if you change headings to standard, then you can define which text will be used for template header. I suppose it could contains some wiki-text that would have the timestamp in format you prefer.

After my test, I found the documentation is wrong. The "headings" should be "page".

In T216858#5191140, @Petrb wrote:

For example:

template-header: "{{CURRENTYEAR}}年{{CURRENTMONTH}}月:"

It works. But I hope the warnings in same month should be merge into single section (Expected result, Actual result).