Convert 2017 January 00:00:00.5912977 to year,month,day,hour,,,,,,seconds, as requested:
dt = datetime('2017 January 00:00:00.5912977', ...
'InputFormat','yyyy MMMM hh:mm:ss.SSSSSSS', ...
'Format','yyyy,MM,dd,hh,,,,,,ss')
Various conversions from MJD 57754, since that was mentioned:
dt = datetime(57754,'Format','yyyy MMMM dd hh:mm:ss.SSSSSSS','ConvertFrom','MJD')
dt = datetime(57754,'Format','yyyy MMMM hh:mm:ss.SSSSSSS','ConvertFrom','MJD')
dt = datetime(57754,'Format','yyyy,MM,dd,hh,mm,ss','ConvertFrom','MJD')
dt = datetime(57754,'Format','yyyy,MM,dd,hh,,,,,,ss','ConvertFrom','MJD')