ClickHouse date/time/timezone changes: v25.8 through v25.12

Summary of all changes to date handling (including date/time/timezone conversion functions) from the 2025 changelog.

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v25.12 (2025-12-18)

New Feature

• Time and Time64 data types are now production ready; enable_time_time64_type is enabled by default. #89345 — changelog line 68

Bug Fixes

• PREWHERE bugs involving supertypes for Time and Time64 data types fixed. #84715 — changelog line 159
• Fix inference of bad DateTime64 values from Strings in text formats. #90013 — changelog line 174
• Time and Time64 now respect timezones correctly when converting from DateTime and DateTime64 (shows time in the same timezone as the user's DateTime view). #90310 — changelog line 191
• Fix bug where SELECT CAST(CAST(now(), 'Time'), 'Time64') produced incorrect result. #90324 — changelog line 192
• Fix toDateTimeOrNull of a negative argument incorrectly returning NULL. #90490 — changelog line 202
• Fix possible logical error during output of LowCardinality(Date32) in Arrow format. #90505 — changelog line 203
• Fix overflow while reading from ORC format for Date and DateTime64 types. #91572 — changelog line 261

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v25.11 (2025-11-27)

Backward Incompatible Changes

• Escape filenames for Variant type subcolumns in Wide data parts. Fixes storing types with special symbols inside Variant (like DateTime with a specific timezone containing \). #87300 — changelog line 300
• Parquet no-timezone timestamps (isAdjustedToUTC=false) are now read as DateTime64(..., 'UTC') instead of DateTime64(...). Use input_format_parquet_local_time_as_utc = 0 for old behavior. #87872 — changelog line 305

Bug Fixes

• (backport) Fix inference of bad DateTime64 values from Strings in text formats. #90013 — changelog line 510

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v25.10 (2025-10-31)

Bug Fixes

• Fixed incorrect handling of pre-epoch dates with fractional seconds in parseDateTime64BestEffort, change{Year,Month,Day}, and makeDateTime64. Previously the subsecond part was subtracted from seconds instead of added. E.g. parseDateTime64BestEffort('1969-01-01 00:00:00.468') returned 1968-12-31 23:59:59.532 instead of 1969-01-01 00:00:00.468. #85396 — changelog line 684
• Fix inferring Date/DateTime/DateTime64 on dates that are out of supported range. #86184 — changelog line 686
• Makes toDate and toDate32 behave the same for all numeric types. Fixes Date32 underflow check during cast from int16. #87176 — changelog line 695
• Fix handling of timestamp / timestamptz columns in Glue catalog. #87733 — changelog line 725
• Fix incorrect granules/partitions elimination for datetime-based keys when using session_timezone setting in queries. #87987 — changelog line 737
• Fix UBSAN integer overflow in accurateCast error message when converting large values to DateTime. #88520 — changelog line 765
• Fix bug where converting DateTime64 to Date with date_time_overflow_behavior = 'saturate' could lead to incorrect results for out-of-range values when working with time zones. #88737 — changelog line 775

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v25.9 (2025-09-25)

Backward Incompatible Change

• Disable nonsensical binary operations with IPv4/IPv6 — disallows operations with floating types that previously threw logical errors with some types (such as DateTime). #86336 — changelog line 797

New Feature

• Aggregate functions timeSeriesChangesToGrid and timeSeriesResetsToGrid (PromQL changes/resets equivalents using timestamp grids). #86010 — changelog line 818

Improvements

• It's no longer possible to specify time zones for the Time type (it didn't make sense). #84689 — changelog line 852
• Simplified (and avoided some bugs) logic related to parsing Time/Time64 in the best_effort mode. #84730 — changelog line 853
• Make the staleness window in timeSeries*() functions left-open and right-closed. #86588 — changelog line 867
• Enable short circuit evaluation for parseDateTime function. #87184 — changelog line 883

Bug Fixes

• Fix function timeSeriesResampleToGridWithStaleness() when the first bucket has no value. #86507 — changelog line 930
• Fix TimeSeries engine table breaking creation of new replica in Replicated Database. #86845 — changelog line 949
• Fix date field populating in system.iceberg_metadata_log table. #86961 — changelog line 954

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v25.8 LTS (2025-08-28)

New Features

• Added function dateTimeToUUIDv7 to convert a DateTime value to a UUIDv7. #84319 — changelog line 1034
• timeSeriesDerivToGrid and timeSeriesPredictLinearToGrid aggregate functions (PromQL deriv/predict_linear equivalents). #84328 — changelog line 1035
• New TimeSeries functions: timeSeriesRange(start_timestamp, end_timestamp, step) and timeSeriesFromGrid(start_timestamp, end_timestamp, step, values). #85435 — changelog line 1036

Improvement

• You can now use Time and Time64 types inside the JSON type. #83784 — changelog line 1104

Bug Fix

• Overflow large values (>2106-02-07) when casting from Date to DateTime64 is fixed. #83982 — changelog line 1189