Or change the post date for any other reason!
"Post Options" is located below and toward the left of the Blogger Editing box. (It's above the "Publish Post" button.) Click it, and you'll notice some boxes that say Post Date and Time appear toward the far right side of the screen.
[More below...Screenshot (click on image to enlarge) plus additional info...]
|OLD (CLASSIC) BLOGGER|
|To keep a post at the top of the blog, either as an Introduction Or Welcome or Index or whatever you'd like to call it, use the "Post Options" to change the date to one in the future. At present, Blogger only lets me advance it to Dec. 31 of next year. I'll have to advance the date again next year. And so on.|
If I'm unclear, check the same info with Chuck at The Real Blogger Status
You can now put a Page Element (gadget) at the top of your blog that will always stay in place without fooling with dates.
You can always relocate the page element again later by drag and drop.