three timestamps/table, use of 'now' in table creation statement

I want to have three timestamps columns in a table:

'created'
'modified'
'archived'

not unlike more modern file systems.

What I want to happen is that all three columns get set with the 'now'
value to the nearest second, and they ALL have the exact same value.

I want to be able to compare 'created' with 'modified'
to see if it's been modified,
I want to be able to compare 'created' with 'archived'
to see if it's been archived.

I don't want to have NULL's with their propagation issues.

Can I use the constant 'now' in the table creation statements?

Will all three columns get assigned the same value at the start of each
record creation, or will I have some that might straddle a second
boundary and be one second apart?

How do I tell the 'now' constant to be to the second's place in
precision?

--

Carpe Dancem ;-)
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Remember your friends while they are alive
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Sincerely, Dennis Gearon