In chrome print preview, under Options tab, the default is having Headers and footers ticked on. Is it not possible to set it default to off via javascript / chrome extension / anything outside telling user to do it manually?
OR is it possible to remove the date displayed there?

In short, yes you can control this behavior. It is actually very bizzarre — as appears to have been originally answered in the question “In Google Chrome, Docs Can Control Headers and Footers from Javascript?” The secret to this behavior is in the
@pageCSS property*.If you set this exact style:
Then you get the desired behavior, the headers & footers option disappears:
This appears to be an undocumented behavior of Google Chrome, or at least not widely known — cursory digging in to their developer docs garnered nothing. Google uses it themselves throughout their own web-apps, so it’s probably not a secret, but I couldn’t find any official notes on it.
Notably, a margin of
0does not simply disable the “headers & footers” option, it actually causes it to disappear from the menu entirely ( by quickly folding ).Experimentation reveals that other variations of this do not have the same effect. For example
margin: 0; margin-left: 10cm;does not cause this behavior.If you do choose to implement this solution, it means forfeiting the ability to control those margins through the
@pageproperty — you should instead be controlling them as part of a CSS print-media stylesheet. Bummer that Chrome kind of destroys the@pageproperty this way. That said,FFstill does not support@page( as of now ) so it’s not a perfect solution to begin with.*More information about the
@pagepropertyThe
@pageCSS is supposed to control the margins of the printed page, the specification says:Most modern browsers support the
@pageCSS property. Firefox is the standout who doesn’t, though they do fully document it in their developer resources, and their issue tracker has a ticket for this that goes back 10 years. The most recent action on it was today, so perhaps FF will provide@pagesupport soon.