When Big Screen EPG processes your data - it is designed to work across multiple Time Zones and correctly handle Daylight Saving changes (assuming your source EPG data has valid start/stop times with timezone specifiers). Then, during the parsing of your XMLTV file - Big Screen EPG will convert your specified start/stop times into Universal Time Code (UTC +00:00) before it sends the data to Media Center.  (as Media Center itself works purely with UTC times).

For example - '20100410000000 +0000' (UTC) is exactly the same as saying '20100410010000 +0100' (Brittish Standard Time with DST) or '20100410100000 +1000' (Australian Eastern Std Time - no DST) in terms of Big Screen EPG - and it doesnt matter at all which one has been used in the xmltv file (its all exactly the same time).
 
Big Screen EPG in fact converts any time into UTC as it's being parsed in so no problem with any of these - and when a MXF file is generated for 7mc everything is output as UTC times at that point.

For more detailed technical information on the appropriate XMLTV time formats supported by Big Screen EPG - see the Help File topic : XMLTV Start/Stop times in Program Elements

Loading in EPG Data in a period leading up to a DST change

Where timezone information has been correctly supplied in your XMLTV start/stop times (ie. times contain ' +/-XXXX' at the end) - then you shouldn't experience any problems with Daylight Savings Time (DST) changes or periods leading up to a DST change (ie. if your DST change is on Saturday night and you are loading in data which contains days before and after the change).

If however - your XMLTV source does not contain any timezone information at all (and only has date/time) - then it's possible you might experience problems with times after the DST change (when loading in data that is before and after a DST change) - as Big Screen EPG will simply assume the current Time Zone is in place. As such it's highly recommended you try to use sources which have the full timezone information supplied.

Effectively Using the TimeZone Shift Minutes Setting on XMLTV Providers

Big Screen EPG provides a special setting (per provider) which allows you to automatically add/subtract a specified number of minutes to your start/stop times. This setting is then applied to all EPG data from that provider - and will be reflected in the Media Center EPG.
 
It's important to note that this setting was added to support scenarios where you are getting EPG data made for a different region (that is timeshifted when 're-broadcasted' in your locale) - which might be the case if you are unable to obtain EPG data for your locale.  This setting however was not designed to be used to handle DST changes (although it might 'appear' to work in certain scenarios) - as loading in EPG data leading up to a DST change would mean that all start/stop time data after this DST change may be invalid