Worked examples
Check the offset against both endpoints.
These examples use exact integer milliseconds and the supported SRT subset. They demonstrate timing arithmetic, not caption quality or player compatibility.
Move two cues 750 ms later
1 00:00:01,250 --> 00:00:03,000 Hello <i>world</i>. A second line. 2 00:00:03,500 --> 00:00:05,125 A later cue.
With offset +750, the timing lines become:
00:00:02,000 --> 00:00:03,750 00:00:04,250 --> 00:00:05,875
The first duration stays 3,000 − 1,250 = 1,750 ms. The second stays 1,625 ms. The gap stays 3,500 − 3,000 = 500 ms. Counters, wording, tag characters and line structure do not change.
Move the same cues earlier, exactly to zero
Offset -1250 produces 00:00:00,000–00:00:01,750 for cue 1 and 00:00:02,250–00:00:03,875 for cue 2. Reaching zero is allowed. Offset -1251 would make the first start negative, so the entire requested shift is rejected. The first cue is not shortened, and the second is not exported alone.
Borrow across a minute
Starting at 00:01:00,000 and ending at 00:01:01,005, a shift of -251 gives 00:00:59,749 through 00:01:00,754. The duration remains 1,005 ms. Integer formatting handles the boundary without fractional-time rounding.
Carry across an hour
A cue from 00:59:59,999 to 01:00:00,010, shifted by +2, becomes 01:00:00,001 through 01:00:00,012. The duration remains 11 ms. Hours do not wrap at 24; this tool supports labels through 99 hours.
Overlaps remain overlaps
If cue 1 ends at 3,000 ms and the next entered cue begins at 2,000 ms, the signed gap is −1,000 ms. Adding 1,000 ms to both cues keeps that gap at −1,000 ms. Cueslide does not sort the cues or remove an overlap. A cue with identical start and end also retains its zero duration.
A timing-like text line stays text
1 00:00:05,000 --> 00:00:06,000 A line of literal text: 00:00:01,000 --> 00:00:02,000 <img src=x onerror=1>
With offset 17, only the structural timing line after counter 1 changes to 00:00:05,017–00:00:06,017. The timing-like body line and markup-looking text remain unchanged and inert. No HTML is executed or styled.
The upper bound is also all-or-nothing
A cue ending at 99:59:59,999 accepts offset 0 but cannot be moved even 1 ms later in this product's two-digit-hour range. The error leaves no current shifted output. The limit is explicit, rather than a silent wrap or a dropped endpoint.
A constant offset does not fix drift
If a subtitle is correctly aligned near the beginning but progressively wrong later, moving every cue by the same amount will not change that difference. No speed conversion or automatic alignment is performed here. Check the result in your intended editor or player.