When the ceasefire was announced in September, President Juan Manuel Santos, also gave the later date. After that, Santos said, it would be extended in line with progress in peace negotiations.
But terms reached in Quito as the parties seek to negotiate peace call for a temporary end of hostilities to hold until January 9 and "not the 12th as some government spokespeople have said," the rebel ELN said in a statement yesterday.
The next phase of the talks hosted by Ecuador in Quito starts October 23.
During his visit this month, the pope met with Santos, who is seeking comprehensive peace.
After the peace deal with the Marxist FARC, the ELN is the last remaining insurgency in what was a complex, five- decade conflict.
It has left 260,000 people confirmed dead, 60,000 unaccounted for and seven million displaced.