Don't label manually at all; use a datetime variable for the x-axis variable in plot() and you'll get datetime ticklabels automagically.
ADDENDUM:
t=1:4383; t=t.';t=t-t(1);
Qobs=randn(size(t));
ts1 = timeseries(Qobs,t);
ts1.TimeInfo.Units='days';
ts1.TimeInfo.StartDate='01-Jan-2000';
ts1.TimeInfo.Format='mmmyy';
plot(ts1)
hAx=gca;
xl=xlim;
xl(2)=xl(2)+days(1);
xlim(xl)
produced
Finish up as desired.
Not knowing what X is, no way to know what to do about adding a bar plot at this point...
NB: The bug/implementation snafu on the TS date format string. Setting it to 'MMMyy' as is correct for datetime object produced warning/error when tried to plot as
>> plot(ts1)
Error using matlab.internal.datetime.cnv2icudf (line 157)
Unrecognized minute format. Format: MMMyy.
Error in timeseries/plot (line 142)
datetimeTickFormat = matlab.internal.datetime.cnv2icudf(char(h.TimeInfo.Format));
>>
Cap-M is minute field for datenum variables, NOT datetime class which is what the timeseries and new-fangled DatetimeRuler object is for the datetime aware plot functions. In fact, after the plot() line above,
>> hAx.XAxis
ans =
DatetimeRuler with properties:
Limits: [Jan 01, 2000 Jan 01, 2012]
TickValues: [Jan 01, 2000 Jan 01, 2002 Jan 01, 2004 Jan 01, 2006 Jan 01, 2008 Jan 01, 2010 Jan 01, 2012]
TickLabelFormat: 'MMMyy'
Show all properties
>>
shows it was converted.