[html] Issue: datetime-local needs a health warning for floating to incremental time conversion (was I18N-ISSUE-89) marked as i18n

chaals has just labeled an issue for https://github.com/w3c/html as 
"i18n":

== datetime-local needs a health warning for floating to incremental 
time conversion (was I18N-ISSUE-89) ==
The HTML5.0 
[issue](https://www.w3.org/Bugs/Public/show_bug.cgi?id=16960) was 
originally closed when the type `datetime-local` was removed from the 
Spec. When that input type was revived recently, the resulting text 
does refer to floating time values. However, the original thread 
included an ask for a "health warning" related to the fact that the 
values in this type are implicitly converted to incremental time 
values with a time zone of UTC. Here are the conversion paragraphs in 
the current draft:

> The algorithm to convert a string to a number, given a string input,
 is as follows: If parsing a date and time from input results in an 
error, then return an error; otherwise, return the number of 
milliseconds elapsed from midnight on the morning of 1970-01-01 (the 
time represented by the value "1970-01-01T00:00:00.0") to the parsed 
floating date and time, ignoring leap seconds.

> The algorithm to convert a number to a string, given a number input,
 is as follows: Return a valid normalized floating date and time 
string that represents the date and time that is input milliseconds 
after midnight on the morning of 1970-01-01 (the time represented by 
the value "1970-01-01T00:00:00.0").

A health warning should make mention of this. Otherwise users might be
 surprised when they enter a "local" wall time and it is later 
returned as a different date or time value because of the difference 
between local wall time and UTC.

See https://github.com/w3c/html/issues/474