from then 与 since that time 有什么区别

from then on
since then
1.中文意思略有不同
from then on 从那时起
since then 从那时起一直到现在
2.谓语时态不同
from then on 谓语用过去时
since then 谓语用现在完成时.
3.例句
From then on I made up my mind to work hard.从那时起,我下定决心好好学习.
Since then I haven't seen him.自从那时起到现在,我就一直没有见到他.