Final Fantasy XV UNCOVERED!
Python (335 bytes)

t=raw_input().replace(*': ').split();x='PMCE'.index(t[2][0]);t[0]=int(t[0])+x;print '%s:%s PM PDT' % tuple(t[:1]);x=t[0]*60+int(t[1]);print ['%s minutes until the pre-show!'%(360-x),'Pre-show started %s minutes ago; UNCOVERED is starting in %s minutes!'%((x-360),(420-x)), 'UNCOVERED started %s minutes ago!'%(x-420)][(x&gt;360)+(x&gt;420)]


Output:

1:00 MDT
2:00 PM PDT
240 minutes until the pre-show!

6:00 CDT  
8:00 PM PDT
UNCOVERED started 60 minutes ago!

6:50 PDT
6:50 PM PDT
Pre-show started 50 minutes ago; UNCOVERED is starting in 10 minutes!