Install & Compatibility
Where this runs
tested against v6.2.4 · pip install
no network on importno background threads
Install × environment matrix
Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux
muslpy 3.10–3.95 runs
installs and imports cleanly · install 0.0s · import 0.068s · 19.1MB
glibcpy 3.10–3.95 runs
installs and imports cleanly · install 1.9s · import 0.062s · 20MB
17MB installed
● package 17MB
Code
Verified usage
Verified import paths — ran on the pinned version, not inferred.
croniter
✓ from croniter import croniter
Demonstrates creating a croniter object and retrieving the next matching datetime. It also shows the `day_or` parameter for 'AND' logic between day-of-month and day-of-week fields.
from datetime import datetime
from croniter import croniter
# Example 1: Every 5 minutes
base = datetime(2010, 1, 25, 4, 46)
iter_5min = croniter('*/5 * * * *', base)
print(f"Next occurrence (every 5 min): {iter_5min.get_next(datetime)}")
# Example 2: Every Monday and Friday at 04:02
base = datetime.now()
iter_mf = croniter('2 4 * * mon,fri', base)
print(f"Next occurrence (Mon/Fri 04:02): {iter_mf.get_next(datetime)}")
# Example 3: First day of the month AND a Wednesday
# (using day_or=False for AND logic, like fcron)
base = datetime.now()
iter_and = croniter('2 4 1 * wed', base, day_or=False)
print(f"Next occurrence (1st day AND Wed 04:02): {iter_and.get_next(datetime)}")
Debug
Known issues
breakingThe `croniter` project was previously declared unmaintained and abandoned by its original author in late 2024 due to concerns about the EU Cyber Resilience Act. It has since been adopted and is now maintained by Pallets-Eco. Users should ensure they are using the `pallets-eco` version and monitor its status if the CRA impacts open source libraries.fixEnsure installation from the official PyPI `croniter` package, which is now maintained by Pallets-Eco, and update to the latest version (6.x.x) if using an older, unmaintained fork.
affects: <= 6.0.0 (original author's branch)
gotchaBy default, `croniter` uses 'OR' logic when both 'day of month' and 'day of week' fields are specified in a cron expression, matching standard Vixie-cron behavior. This means a schedule will trigger if *either* the day of month *or* the day of week matches. For 'AND' logic (trigger only if *both* match, like fcron), you must explicitly pass `day_or=False` to the `croniter` constructor.fixIf 'AND' logic is desired for day and day-of-week fields, initialize `croniter` with `croniter(cron_expression, base, day_or=False)`.
affects: All versions
gotcha`croniter` is less strict than some cron implementations regarding ranges for months (e.g., 'APR-JAN') and days of the week (e.g., 'SAT-SUN', 'WED-SUN'). These reverse ranges are interpreted, which might lead to unexpected iterations if a strict cron parser is anticipated.fixCarefully review cron expressions, especially those with reverse ranges. Validate the generated iterations against expected behavior, or use a more strictly validated cron string if precise adherence to a specific cron flavor is critical.
affects: All versions
gotchaThe `is_valid()` method, by default, only performs basic syntax and field range validation. It does not perform cross-field validation (e.g., it will report '31 2 * * *' as valid even though February has no 31st). To enable strict cross-field validation, you must pass `strict=True`.fixAlways use `croniter.is_valid(cron_expression, strict=True)` for comprehensive validation, especially with user-provided cron strings, to prevent parsing impossible dates.
affects: All versions
gotchaThe `croniter.match()` method has a default precision of 60 seconds for 5-field expressions and 1 second for 6-field expressions. This means a target `datetime` up to 60 (or 1) seconds *after* the scheduled time will still be considered a match. This can cause issues in scenarios requiring exact time matching.fixWhen using `croniter.match()`, be aware of its default precision. For highly precise matching, consider comparing `datetime` objects directly or adjusting the comparison logic.
affects: All versions
Errors
Common errors & fixes
ModuleNotFoundError: No module named 'croniter'
The 'croniter' library is not installed in the Python environment where the code is being executed.
fixInstall the croniter package using pip: `pip install croniter`
croniter.croniter.CroniterBadCronError: Exactly 5 or 6 columns has to be specified for iterator expression.
The provided cron expression string is malformed and does not contain the required 5 fields (minute, hour, day of month, month, day of week) or 6 fields (including seconds).
fixEnsure your cron expression has either 5 or 6 space-separated fields. For example, '0 0 * * *' for daily at midnight, or '0 0 0 * * *' for daily at midnight with seconds.
ValueError
This generic error can be raised by `croniter` for various reasons, such as providing an invalid character in a cron field, specifying a number outside the valid range for a field (e.g., month 13), or using an invalid cron step (e.g., '0-10/error').
fixCarefully review the cron expression for any invalid characters, out-of-range numbers, or incorrect syntax. Use `croniter.is_valid(cron_expression)` for pre-validation or consult cron syntax documentation.
croniter.croniter.CroniterBadDateError: failed to find next date
The `croniter` library could not find a matching next (or previous) date for the given cron expression within its default search window (typically 50 years). This often happens with very sparse or impossible cron expressions, like '0 0 29 2 *' when the `base` date is in a non-leap year and the next valid date is too far in the future.
fixFor very sparse cron expressions, consider increasing the `max_years_between_matches` parameter in the `croniter` constructor (e.g., `croniter(cron_expression, base, max_years_between_matches=200)`). Alternatively, ensure the cron expression is feasible given the `base` datetime.
TypeError: Invalid ret_type, only 'float' or 'datetime'
When calling methods like `get_next()` or `get_prev()`, an invalid type was passed to the `ret_type` argument. `croniter` expects either `float` or `datetime.datetime`.
fixEnsure that the `ret_type` argument, if provided, is either `float` or `datetime.datetime`. For example: `iter.get_next(datetime.datetime)` or `iter.get_next(float)`.
Upgrade
Version history
6.2.4latest on PyPI · released Jul 10, 2026
Audit
Dependencies
python-dateutilrequiredRequired for date and time parsing and manipulation.
pytzoptionalRecommended for handling timezones, especially with older versions or complex DST scenarios.