When two sources conflict on something as important as a release date, go with the government source every time.
The official state department of corrections or Bureau of Prisons inmate locator pulls directly from the system that actually manages the sentence calculation. That database reflects the official record, including good time credits, any adjustments that have been made, and the current projected release date as calculated by the corrections department itself. It is the most authoritative source available to the public.
InmateAid's inmate locator is populated in part by information submitted by members of the community, which means it can lag behind official updates or reflect outdated information that has not been corrected. It is a useful starting point for finding someone, but for official dates and status, the government database is where the accurate information lives.
The April date on the government site is almost certainly the correct one. A release date of tomorrow that does not match what the official system shows is most likely an outdated entry or an error in the third-party profile.
If you want InmateAid to look into the specific discrepancy and verify what the official record shows, send an email to aid@inmateaid.com with the inmate's name and any identifying information you have. The team will investigate and get you a clearer picture.
In the meantime, do not make plans around the date tomorrow until you have verified it against the official government source. Getting that wrong in either direction, showing up expecting a release that does not happen, or being caught off guard by one that does, is a situation worth avoiding.