Convert dates to julian day number in astropy? I'm using astropy and I need to convert dates like this: 
2012.06.22_17:56:15_TAI
into julian day number. I tried:

from astropy.time import Time
hmitime = hminew['MidTime']
i=0
print(hmitime[i])
hmi0=Time(hmitime[i],scale='tai')
print(hmi0.jd)


where hmitime it's just the matrix with my dates. But python shows me this:

ValueError: Input values did not match any of the formats where the format keyword is optional [u'datetime', u'iso', u'isot', u'yday', u'fits', u'byear_str', u'jyear_str']


Does anyone know what is wrong? How can I convert my dates??
Thanks
The accepted string formats for date-hms are:

Format  Class    Example argument

fits    TimeFITS    ‘2000-01-01T00:00:00.000’
iso     TimeISO     ‘2000-01-01 00:00:00.000’
isot    TimeISOT    ‘2000-01-01T00:00:00.000’


https://docs.astropy.org/en/stable/time/index.html

You can either change one of these, or you can define your own format by deriving a class for the format from the TimeFormat class.
https://docs.astropy.org/en/stable/api/astropy.time.TimeFormat.html#astropy.time.TimeFormat