Formula for Date/Time Field

[bbrouard]

I'm looking to build a formula for a date/time field where the date varies but the time is consistent. When I try to do this, I encounter errors. 

Goal:
Have the date be for "today" (whatever date that is) but the time be 14:00 EST. 

Attempted Formula:
DATETIMEVALUE(TEXT(TODAY()) + ' 18:00:00')

Error Message:
There seems to be a problem with the formula syntax, please check it over and try again.

How can I build a formula that will reach my goal?