ISTIME in Calligra Sheets: Identify time-formatted values

ISTIME is a type test useful for shift schedules, opening-hour records or imported time columns. A TRUE result means the evaluated value carries a time or date-time format tag in the examined Calligra 26.08.2 implementation. It does not mean a piece of text looks like a clock time, and it does not confirm that an employee’s recorded working hours satisfy any business rule.

The handbook includes ISTIME("12:05") returning TRUE. However the version-pinned implementation checks Value::fmt_Time or Value::fmt_DateTime, so quoted strings cannot safely be promised to behave identically before confirming the formula engine’s coercion. The discrepancy is particularly important for pasted CSVs and locale-specific time strings.

=ISTIME(x)

Return is Boolean. KDE’s ISTIME documentation defines a one-argument function; the pinned callback returns TRUE on fmt_Time or fmt_DateTime. No argument is optional and no default time or timezone is defined.

Construct time values with the documented TIME function to avoid ambiguous typed strings.

Now enter in a separate column:

B2: =ISTIME(A2)
B3: =ISTIME(A3)
B4: =ISTIME(A4)

The independently reasoned, source-inferred expected Boolean outputs are TRUE, FALSE, FALSE respectively, provided the function result maintains its time-format tag when evaluated. In Calligra source, TIME constructs a time object (Time res(h,m,s); return Value(res);). See the official TIME XML and pinned TIME code. Output display 12:05, 12:05:00 or another locale form is not guaranteed; the test concerns the value type.

An advanced data-quality column

If A2:A30 holds typed shift-start times and values pasted from outside sources, put in B2:

=IF(ISTIME(A2);"Typed time";"Check imported value")

Copy the formula down. The reasoned expected labels for the sample A2, A3, A4 are Typed time, Check imported value, Check imported value, assuming standard IF behavior. This flags suspect imported records without coercing strings or modifying the source values. It does not measure shift duration; add a separate calculation for that.

Advanced case: a date-time may satisfy two tests

Both ISDATE and ISTIME accept fmt_DateTime in the pinned code. Thus a genuinely typed date-time can be source-inferred to return TRUE for both tests. This is intentional, not contradictory: the same value contains both date and clock-time components. A time-only value is not necessarily a date. To mark entries that include both, the following is a documentation/source-based candidate that still requires native checking:

=IF(AND(ISDATE(A5);ISTIME(A5));"Date and time";"Not a combined datetime")

Do not infer A5’s internal tag from its visual formatting or a string representation alone.

• A displayed 12:05 is rejected: check if the value is a text string rather than a time type; the callback does not parse clock text itself.
• Copy/paste changed behavior: verify whether the data was pasted as text, as an underlying time, or as a number with display formatting.
• ISTIME("12:05") disagrees with the handbook: log the exact release, locale and input method; this handbook example predates 26.08.2 and cannot replace execution evidence.
• Blank, error and malformed inputs: exact error propagation has not been natively determined. Do not promise particular Calligra error strings.
• Crossing midnight: ISTIME only identifies a type; it cannot say whether a 23:30 shift ended the same day as its starting date.

Microsoft’s Excel standard IS-functions reference does not list ISTIME; Excel stores many time values numerically. An Excel formula such as ISNUMBER would answer a different question: whether a value is numeric, not whether it contains a Calligra time-format tag. Avoid mechanically translating ISTIME to ISNUMBER. Other spreadsheet packages require separately checked functions and value models; this guide only establishes Calligra’s documented/source-scoped behavior.

Reviewed KDE ISTIME, KDE TIME and source at release commit 26.08.2, accessed 2026-10-12. Related external references were checked.