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iCalendar conversion problem

Fix CSV-to-ICS Date and Time Errors

Prepare event dates, times and identifiers for iCalendar conversion and verify time zones and all-day event boundaries.

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CSV to ICS

Open CSV to ICS

What the error actually means

iCalendar distinguishes DATE values from DATE-TIME values. RFC 5545 examples also show UID, DTSTAMP and DTSTART in VEVENT records, and DTEND is non-inclusive for all-day events. Ambiguous local times can import at the wrong hour even when the ICS syntax is valid.

Likely causes

  • The CSV mixes day-first and month-first dates.
  • Local times have no documented time zone.
  • An all-day end date was treated as inclusive.
  • Rows lack a stable event identifier or summary mapping.

All-day boundary

Problem

One-day event with DTSTART;VALUE=DATE:20260820 and DTEND;VALUE=DATE:20260820

Correct pattern

DTSTART;VALUE=DATE:20260820 and non-inclusive DTEND;VALUE=DATE:20260821

A safe repair workflow

  1. 1Use YYYY-MM-DD for all-day dates, or ISO timestamps with Z or a timezone offset. An all-day end date is exclusive. Ambiguous dates are rejected.
  2. 2Normalize source dates without guessing ambiguous values.
  3. 3Decide whether each row is all-day or timed.
  4. 4Map summary, start, end and optional location fields.
  5. 5Import a sample into the actual calendar and inspect several time zones.

How to verify the result

A file that downloads successfully is not automatically a correct file. Check the result at both the structural and business-data levels:

  • All-day events occupy the intended dates.
  • Timed events appear at the intended local hour.
  • End times occur after start times.
  • Repeated imports do not create unintended duplicates.

Read the deeper guides

Convert a CSV Event List to ICS Without Shifting the TimesPrepare spreadsheet events for calendar import, handle dates and time zones safely, and check the ICS file before adding it to Google, Outlook, or Apple Calendar.How to Clean CSV Data Without Hiding the Original ProblemsLearn practical techniques to clean messy CSV files. Remove duplicates, fix formatting, and standardize data without Excel crashes or complex scripts.

Official references

Platform requirements and technical standards can change. These are the primary references used for this page.