specific day. T-Mobile has already announced that it will be releasing the phone online April 24th and in stores May 1st. AT&T has an April 30th release date and Sprint will launch the phone on April 27th.
Verizon's tweet means that the phone could conceivably launch on May 1st, but if the previously leaked information holds true, don't expect to see the Samsung Galaxy S4 at your local Verizon store until the end of next month. As we noted before, the carrier is known for rigorously testing its phones.
source: Verizon via AndroidCentral