The Syrian Defense Ministry released a statement on December 29 that a nationwide ceasefire between government forces and armed opposition groups will take place on December 30 (00:00 local time).
The ceasefire agreement excludes Jabhat Fatah al-Sham (formerly Jabhat al-Nusra, the Syrian branch of al-Qaeda) and ISIS terrorist groups.
The Syrian government and armored opposition groups (a full list is unknown now) signed 3 three documents on the issue (more here).
Official statement:
Click to see the full-size image