pandas-dev/pandas · error · ValueError

left and right must have the same time zone, got

Error message

left and right must have the same time zone, got '{left.tz}' and '{right.tz}'

What it means

Raised when both left and right are DatetimeIndex but their time zones differ (compared by `str(left.tz) != str(right.tz)`). IntervalArray requires tz-aware endpoints to share one timezone so the resulting dtype is unambiguous.

Solutions

1. Localise or convert both sides to the same tz: `right = right.tz_localize('UTC')` (if naive) or `right = right.tz_convert(left.tz)` (if aware).
2. Strip tz from both sides if naive comparison is acceptable: `left.tz_localize(None)`, `right.tz_localize(None)`.
3. Verify equality with `str(left.tz) == str(right.tz)` before constructing.

Example fix

# before
l = pd.date_range('2020', periods=2, tz='UTC')
r = pd.date_range('2020', periods=2, tz='US/Eastern')
IntervalArray.from_arrays(l, r)

# after
IntervalArray.from_arrays(l, r.tz_convert('UTC'))

import pandas as pd

def unify_tz(left, right, target='UTC'):
    if getattr(left.dtype, 'tz', None) or getattr(right.dtype, 'tz', None):
        if left.tz is None:
            left = left.tz_localize(target)
        if right.tz is None:
            right = right.tz_localize(target)
        left = left.tz_convert(target)
        right = right.tz_convert(target)
    return left, right

import pandas as pd

def same_timezone(left, right) -> bool:
    lt = getattr(left, 'tz', None)
    rt = getattr(right, 'tz', None)
    return str(lt) == str(rt)

try:
    arr = IntervalArray.from_arrays(left, right)
except ValueError as e:
    if 'same time zone' in str(e):
        right = right.tz_convert(left.tz) if right.tz else right.tz_localize(left.tz)
        arr = IntervalArray.from_arrays(left, right)
    else:
        raise

When it happens

Trigger: left tz-aware UTC, right naive or tz-aware US/Eastern; mixing timestamps parsed with different `tz_localize`/`tz_convert` calls; one side from a tz-aware column, the other from a UTC database field.

Common situations: ETL pipelines combining sources with different timezone conventions; DST-handling refactors; one side accidentally stripped of tz via `.dt.tz_localize(None)`.

Related errors

• Cannot directly set timezone. Use tz_localize() or…
• Cannot modify read-only array
• closed keyword does not match dtype.closed
• invalid dtype
• left and right must have the same length

AI-assisted analysis of pandas-dev/pandas@3b7651241d (2026-08-11). Data as JSON: /api/errors/ce02c3ab5c8509a9. Report an issue: GitHub.

Appendix: source

Thrown at pandas/core/arrays/interval.py:343

            isinstance(left.dtype, CategoricalDtype)
            or is_string_dtype(left.dtype)
            or is_string_dtype(right.dtype)
        ):
            # GH 19016, GH 66518: reject unsupported right-side dtypes too.
            msg = (
                "category, object, and string subtypes are not supported "
                "for IntervalArray"
            )
            raise TypeError(msg)
        if isinstance(left, ABCPeriodIndex):
            msg = "Period dtypes are not supported, use a PeriodIndex instead"
            raise ValueError(msg)
        if isinstance(left, ABCDatetimeIndex) and str(left.tz) != str(right.tz):
            msg = (
                "left and right must have the same time zone, got "
                f"'{left.tz}' and '{right.tz}'"
            )
            raise ValueError(msg)
        elif needs_i8_conversion(left.dtype) and left.unit != right.unit:
            # e.g. m8[s] vs m8[ms], try to cast to a common dtype GH#55714
            left_arr, right_arr = left._data._ensure_matching_resos(right._data)
            left = ensure_index(left_arr)
            right = ensure_index(right_arr)

        # For dt64/td64 we want DatetimeArray/TimedeltaArray instead of ndarray
        left = ensure_wrapped_if_datetimelike(left)
        left = extract_array(left, extract_numpy=True)
        right = ensure_wrapped_if_datetimelike(right)
        right = extract_array(right, extract_numpy=True)

        if isinstance(left, ArrowExtensionArray) or isinstance(
            right, ArrowExtensionArray
        ):
            pass
        else:
            lbase = getattr(left, "_ndarray", left)

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