GDAE and CGDA (both are fifths tuning) are the most popular tunings for tenor guitar. It's a fair bet the fellow who gave you the baritone uke tuned GDAE used it like a (slightly smaller) tenor guitar. Fifths tuning is common with a lot of stringed instrruments including tenor guitar/banjo, mandolin and violin.
All of my instruments including the ukuleles are tuned in fifths, mainly CGDA. This way, playing any one of them reinforces muscle memory and makes transition from one to another easier. When I had a baritone uke, it too was tuned in fifths.
If you like the sound with the GDAE, there's no pressure to change. If the size is comfortable, checking out tenor guitar and tenor banjo may be something to consider in the future.
Last edited by SteveZ; 04-20-2017 at 01:37 AM.
Ukuleles: Martin T1K (T), Oscar Schmidt OU28T (T8), Lanikai LU-6 (T6), RISA Solid (C), Effin UkeStart (C)
Banjo-Ukes: The Duke (T), Lanikai LB6-S (S)
Tenor Guitars: Martin 515, Blueridge BR-40T
Tenor Banjo: Deering Goodtime 17-Fret
Mandolin: Burgess (#7)
The inventory is always in some flux, but that's part of the fun.