First, check if the error is constant.
The opening, middle, and closing subtitles are all about half a second late. You can try using an overall offset, setting the offset to -500 milliseconds. If the opening is aligned but the ending is increasingly off, the problem might be with the time base, the cut version, or a change in pacing. A single offset can only align a specific point and cannot fix the entire timeline.
This tool only adds or subtracts the same start and end times for each subtitle, preserving the original duration and text. It does not perform speech recognition, rewrite dialogue, or pretend to know which frame the subtitle should appear in.
What SRT content does the tool accept?
Each block consists of a numerical sequence number, start and end times, and at least one line of text, separated by blank lines. Time is expressed in HH:MM:SS,mmm; the first version also accepts milliseconds separated by decimal points and consistently exports commas. Minutes and seconds must be between 00 and 59, and the end time must be later than the start time.
Exporting will renumber the text in the current order, preserving the original text lines and tags. The tool will not interpret subtitle style tags, re-wrap, or convert ASS, LRC, or WebVTT. Importing files will read them in UTF-8 format; if garbled characters appear in older encoded files, they should first be converted to UTF-8 in a trusted local editor.
Why would negative time reject the entire output?
A subtitle starting at 00:00:00,200 will have a negative start time if it's moved forward 500 milliseconds. Simply clipping it to zero will shorten the display duration, while deleting it will result in lost content. Therefore, the tool reports the specific subtitle position and preserves the original input, allowing you to process the opening subtitle first or use a smaller offset.
Offsets are in integer milliseconds, ranging from the nearest 24 hours. Crossing seconds, minutes, and hours will be rounded up. Existing overlap between subtitles will be preserved; the tool will not mistakenly treat these overlaps as part of a larger offset, which can be addressed by this method.
You must check three places after exporting.
Using the same video version, find an easily identifiable sentence or lyric at the beginning, middle, and end to check the entry and exit points. Then check if the Chinese text is correct, if line breaks are appropriate, and if long sentences obscure the screen. A calculator displaying "success" only indicates that the time format conversion is complete, not that the audio/video calibration has been performed.
You can first use the two examples on this site: add 500 to 00:00:01,000 to 00:00:02,500 to get 00:00:01,500 to 00:00:03,000, the duration is still 1.5 seconds. The original and adjusted subtitles are retained for easy comparison and rewinding.