Follow up:
I am lazy so i asked my yellow rubber duck (chatgpt). And here is its answer, and because it is deep AI, check everything below (sometimes it makes silly mistakes that look like THE truth):
- Compute Up Vector (Zenith)
Given latitude (ϕϕ) and longitude (λλ), the up vector in ECEF (Earth-Centered, Earth-Fixed) coordinates is:
UpVector=(cos(ϕ)cos(λ),cos(ϕ)sin(λ),sin(ϕ))
UpVector=(cos(ϕ)cos(λ),cos(ϕ)sin(λ),sin(ϕ))
Where:
ϕϕ = Latitude in radians.
λλ = Longitude in radians.
- Compute Local Sidereal Time (LST) for Correct Skybox Rotation
To align the skybox properly with the stars, we need Local Sidereal Time (LST).
Step 1: Compute Julian Date (JD)
First, convert UTC date and time to Julian Date (JD) using:
JD=367Y−⌊7(Y+⌊M+912⌋)4⌋+⌊275M9⌋+D+1721013.5+UT24
JD=367Y−⌊47(Y+⌊12M+9⌋)⌋+⌊9275M⌋+D+1721013.5+24UT
Where:
Y,M,DY,M,D = Year, month, and day.
UTUT = Universal Time (hours, fraction included).
Example: If it's February 3, 2025, at 12:00 UTC, calculate JD for that timestamp.
Step 2: Compute Greenwich Mean Sidereal Time (GMST)
GMST=280.46061837+360.98564736629(JD−2451545)
GMST=280.46061837+360.98564736629(JD−2451545)
This gives the GMST in degrees.
Step 3: Convert GMST to Local Sidereal Time (LST)
LST=GMST+λ
LST=GMST+λ
λλ is longitude in degrees (positive east, negative west).
-
Compute Skybox Rotation
The HDRI skybox rotation (Yaw) should match LST in degrees.
Convert to radians if needed:
Yaw=LSTmod 360
Yaw=LSTmod360
The up vector gives the correct tilt, and the LST gives the proper skybox rotation.
Final Steps in UE5
Up Vector: Controls the HDRI tilt.
Yaw (LST): Controls the HDRI rotation.
Use SetActorRotation on the skybox.
This should correctly align your HDRI skybox to time and location on Earth. 
ps.
Use this reply from out future overlords as guide, you have all keywords, and algorithm how to calculate it. So use google for more reliable articles.
And pps:
I already found derp mistake in last step: do not use set actor rotation for the skybox, instead rotate camera vector in material just like i posted in previous reply.