You are right, it is the space that is throwing things off. So you just just need to put the whole file mask in quotes, and it will work.
So assuming you're using C#...transferOptions.FileMask = "\"*.xml<=" + strTimeMask + "\"";
Which translates to...
"*.xml<=2015-02-04 03:27:11" as your mask
No, the quotes may not be there, they actually break the mask.
This is the correct code:
transferOptions.FileMask = "*.xml<=" + strTimeMask;
If you have a different experience, please attach a full session log file showing the problem (using the latest version of WinSCP).
To generate the session log file, set
Session.SessionLogPath. Submit the log with your post as an attachment. Note that passwords and passphrases not stored in the log. You may want to remove other data you consider sensitive though, such as host names, IP addresses, account names or file names (unless they are relevant to the problem). If you do not want to post the log publicly, you can mark the attachment as private.