about starting date of postdoc I have been accepted for postdoc position. According the detail of postdoc 


  the successful candidate will begin in January 2019


What does it mean? Can I start my work at any time of January? Am I right?
I would presume that you have to inquire with the lab/director/hiring manager/program manager to fix the actual start date by mutual agreement. You can't normally just choose unilaterally, and they may have a fixed date in mind. In general, the hiring entity decides on the employee's start date.