The date you last updated any of your hubs is printed on every hub and you can also find it on your Stats Page. On your Stats Page, just look at the last column labeled at the top, “Changed.” The next column is the “Featured” column. Look for the date in the “changed” column across from the title of the hub you are interested in.
To find that same date on your hub, go to the area just above where readers can vote on your hub, up or down, useful, funny, awesome, beautiful, or interesting. The date you last updated is directly above this section and to the right.
Comments do not cause that date to change. Only changes to photos, maps, text (even just punctuation or a change in a few words), or adding or subtracting capsules for various purposes will cause that date to change.
You cannot see the date of your last update in the “edit” mode. You must be looking at the hub like any other reader to see it.
When Google lists the latest date that you have updated your article, it will list that date above the voting section and that is also in the “changed” column on your Stats Page. Google doesn’t always list that date, or any date, in the description of your hub on their search page, but sometimes it does. I do not know why that date is sometimes listed on Google and sometimes (most often) not.
I hope this will be helpful to you.