hi there, i have a question that is troubling me

Let´s say i create a page called How to build a car
It get indexes on Jan 1st

I then changed the content of the page why would google show the new content with the old date of Jan 1st

I´ve researched this and people say it´s a glitch in how Google works. Surely if the page is indexed Jan 1st and the content updates the indexing date should change

can anyone explain

many thanks

richard