Bit difficult to tell from a sunset.
Dear .. don't worry don't feel sad for that .. I have the same problem .. whenever i meet someone for the first time she/he keeps telling me i am 30-31-32 but i am only 26 that's because i am tall 190 cm and bald .. sometimes i feel very very very depressed as i have to work for many hours to have a decent life .all i can tell you is don't listen much to their words or you will die in pain . people will kill you with their words where you go you will find this kind of people . people who don't know that " words cuts deeper than swords " . however .. Goodluck .
thats not good. if i were them i would try not to act surprised, but then i'm usually able to tell someone's age by looking at them