VisualSubSync is a free open-source application for synchronizing subtitles with video media. It offers a series of features that allow users to easily synchronize and fine-tune subtitles with audio and video. It is especially useful for fansubbers and video editors who need to adjust or correct subtitles to match audio and video. VisualSubSync offers various features that make the process of synchronizing subtitles easier and faster, such as automatic synchronization, manual synchronization, frame-accurate editing, spell checking, and support for many of the most popular subtitle formats. Additionally, the application has a built-in video player with subtitle preview, allowing users to preview the results of their changes before saving.
Discontinued official website no longer available
Suspended the latest version is 3.0.0.4 (09/23/2005, 650Ko, with its Delphi source code): it can still be downloaded from SourceForge.
I had subs with a good language but an incorrect timeline and a sub with a good timeline but an incorrect language, SE's "sync point" did the 20/20 trick perfectly.