The user's problem is a classic case of a modern data need colliding with legacy tool limits. They need to find overlapping date ranges across 12 events, can't use macros, and already tried a brute-force date-list approach that wrecked performance. That's not a user failure, it's a tool failure. The spreadsheet was never built to think in ranges; it was built to think in cells. When your workflow demands pattern detection across intervals, a grid of static values stops being helpful and starts being the obstacle.
The practical takeaway is this: the solution doesn't require more complexity, it requires a smarter approach to the data structure itself. Traditional spreadsheets force you to flatten overlapping ranges into individual dates, which multiplies rows and drags down performance. But if you reframe the problem as a set of intervals, you can use a helper column with a conditional logic formula that flags overlap without exploding the data set. Something like `=SUMPRODUCT((Start<=[End])*(End>=[Start]))>1` for each row can identify overlapping events in a single pass. No macros, no generated date lists, no slowdown. The user's intent is correct, only input should be adding or removing events, but the method needed to match the tool's strengths, not fight its weaknesses.
We think this highlights a broader truth about data work today. Users are being asked to do more with spreadsheets than the original design ever anticipated. The fact that a reasonable attempt to find duplicates collapsed performance isn't a sign the user needs better scripting skills, it's a sign the tool lacks native range-awareness. That's why we're focused on AI-native approaches that treat data as relationships, not just coordinates. A spreadsheet that understands intervals, not just cells, would let you ask "which dates overlap?" and get an answer without building a workaround.
For now, the practical fix is a formula-based overlap flag and conditional formatting that reads it. The user gets the color-coded calendar they need, the worksheet stays fast, and the only input remains adding or removing events. That's not a hack, it's the right solution for the tool they have. But it shouldn't require a forum post to discover.