Cannot parse date troubleshooting

Common issues and solutions for date parsing problems in ClickHouse and Tinybird.

Common errors

CANNOT_PARSE_DATE

Error: CANNOT_PARSE_DATE: Cannot parse date from string "invalid_date"

Cause: Date string in unexpected format

Solution: Use proper date format or handle invalid dates

-- Handle invalid dates
SELECT toDateOrNull(date_string) as safe_date
FROM events

CANNOT_PARSE_DATETIME

Error: CANNOT_PARSE_DATETIME: Cannot parse DateTime from string "invalid_datetime"

Cause: DateTime string in unexpected format

Solution: Use proper DateTime format

-- Use specific format
SELECT toDateTime(date_string, 'YYYY-MM-DD HH:MM:SS') as parsed_datetime
FROM events

Date format issues

Unexpected date formats

Issue: Dates in non-standard format

Solution: Use parseDateTimeBestEffort or specific format

-- Use best effort parsing
SELECT parseDateTimeBestEffort(date_string) as parsed_date
FROM events

-- Or use specific format
SELECT toDateTime(date_string, 'MM/DD/YYYY HH:MM:SS') as parsed_date
FROM events

Timezone issues

Issue: Dates with timezone information

Solution: Handle timezones explicitly

-- Parse with timezone
SELECT toDateTime(date_string, 'UTC') as utc_datetime
FROM events

Data validation

Mixed date formats

Issue: Same column has different date formats

Solution: Handle multiple formats

-- Handle multiple date formats
SELECT 
  CASE 
    WHEN toDateOrNull(date_string) IS NOT NULL THEN toDate(date_string)
    WHEN parseDateTimeBestEffort(date_string) IS NOT NULL 
      THEN toDate(parseDateTimeBestEffort(date_string))
    ELSE NULL
  END as parsed_date
FROM events

Invalid date values

Issue: Date strings that can't be parsed

Solution: Use safe parsing functions

-- Use safe parsing
SELECT toDateOrNull(date_string) as safe_date
FROM events
WHERE toDateOrNull(date_string) IS NOT NULL

Best practices

  1. Use safe parsing - Use toDateOrNull() instead of toDate()
  2. Handle timezones - Be explicit about timezone handling
  3. Validate dates - Check date format before parsing
  4. Use consistent formats - Standardize date formats in data
  5. Handle edge cases - Account for invalid or missing dates