If your subtitles are "out of sync" you can use keyboard shortcuts to "time-shift" subtitles:
Ctrl+Left/Right-arrow:
. Subtitles time correction -/+
(VobSub subtitles dec/inc delay)
Shift+Left/Right-arrow:
. Subtitles time correction -/+ (small steps)
(VobSub subtitles dec/inc speed)
(Also some skins have buttons just to do that.)
If you have BSPlayer Pro, you can also use its in-built subtitle-editor to change (text) subtitle-files permanently.
If you're using BSPlayer's Free version and still wish to permanently "time-shift" or "time-stretch" or "time-shrink" subtitles: there are several (free) subtitle-utilities available which can assist you at that. I personally always use
Vladimir's subsync which is a very simple and basic utility, which does the job it is supposed to do perfectly for only three (text-based) types of subtitlefiles, i.e. SAMI, SubRib and MicroDVD or .smi, .srt and .sub. (For some indication on its use perhaps see
this post).
Other subtitle utilities are (i.a.)
Subtitle Workshop,
Subtitles Translator or
Winsubtitler (which is the successor of SubMax, the development of which is discontinued).