A BaZi chart contains four pillars based on your:
year, month, day and hour of birth.
Each pillar contains a Heavenly Stem and an Earthly Branch.
The Heavenly Stem of your Day Pillar is your Day Master.
There are ten possibilities, created from the Five Elements — Wood, Fire, Earth, Metal and Water — each appearing in Yin or Yang form.
So Astralway might identify you as a:
Yin Water Day Master
or
Yang Wood Day Master.
Your Day Master is an important reference point, but it isn't your entire Chinese chart or simply a Chinese version of your Sun sign.
Its meaning depends on the season and elemental environment surrounding it.