@@ -161,6 +161,7 @@
         "service",
         "service_production",
         "source",
+        "subscriptions",
         "testing",
     }
 )
 
@@ -0,0 +1,91 @@
+"""AdCP 3.3 principal-level reporting subscriptions (experimental).
+
+``media_buy.reporting_subscriptions`` lets a caller register reporting once on
+its principal through ``sync_principal`` instead of once per account through
+``sync_accounts``. This package holds the parts both sides share:
+
+* :func:`expected_subscription_periods` -- the pure coverage rule. A buyer runs
+  it from its own records to learn exactly which periods it is owed; the
+  seller runtime runs it over the same facts to decide which obligations it
+  owes.
+* :func:`resolve_subscription_offerings` -- deterministic selector resolution
+  (``exact`` / ``finest`` / ``all``, ties to the lowest ``offering_id``).
+* :func:`subscription_capabilities` -- the capability fields a seller that
+  serves subscriptions must advertise.
+"""
+
+from __future__ import annotations
+
+from adcp.reporting.subscriptions.capabilities import (
+    REPORTING_SUBSCRIPTIONS_FEATURE,
+    REPORTING_SUBSCRIPTIONS_SECTION,
+    ReportingSubscriptionSupport,
+    advertise_reporting_subscriptions,
+    reporting_configuration_tasks,
+    subscription_capabilities,
+    with_subscription_dimensions,
+)
+from adcp.reporting.subscriptions.coverage import (
+    AccountTimezoneChange,
+    ExpectedSubscriptionPeriod,
+    SubscriptionAuthorization,
+    SubscriptionBuy,
+    SubscriptionBuyFlight,
+    SubscriptionBuyPackage,
+    SubscriptionException,
+    SubscriptionVersionWindow,
+    expected_subscription_periods,
+    subscription_covers_account,
+    subscription_exceptions,
+    subscription_version_windows,
+)
+from adcp.reporting.subscriptions.resolution import (
+    STANDARD_REPORTING_DIMENSIONS,
+    SubscriptionDestination,
+    SubscriptionMatch,
+    SubscriptionOffering,
+    SubscriptionResolution,
+    SubscriptionSelector,
+    resolve_subscription_offerings,
+)
+from adcp.reporting.subscriptions.wire import (
+    project_offering,
+    project_reporting_delivery,
+    project_subscription_coverage,
+    project_subscription_state,
+    serves_settled_subscription_fields,
+)
+
+__all__ = [
+    "REPORTING_SUBSCRIPTIONS_FEATURE",
+    "REPORTING_SUBSCRIPTIONS_SECTION",
+    "STANDARD_REPORTING_DIMENSIONS",
+    "AccountTimezoneChange",
+    "ExpectedSubscriptionPeriod",
+    "ReportingSubscriptionSupport",
+    "SubscriptionAuthorization",
+    "SubscriptionBuy",
+    "SubscriptionBuyFlight",
+    "SubscriptionBuyPackage",
+    "SubscriptionDestination",
+    "SubscriptionException",
+    "SubscriptionMatch",
+    "SubscriptionOffering",
+    "SubscriptionResolution",
+    "SubscriptionSelector",
+    "SubscriptionVersionWindow",
+    "advertise_reporting_subscriptions",
+    "expected_subscription_periods",
+    "reporting_configuration_tasks",
+    "resolve_subscription_offerings",
+    "subscription_capabilities",
+    "subscription_covers_account",
+    "subscription_exceptions",
+    "subscription_version_windows",
+    "with_subscription_dimensions",
+    "project_offering",
+    "project_reporting_delivery",
+    "project_subscription_coverage",
+    "project_subscription_state",
+    "serves_settled_subscription_fields",
+]
@@ -0,0 +1,281 @@
+"""The period calendar shared by subscription coverage on both sides of the wire.
+
+``core/reporting-schedule.json`` ``period_generation``: every boundary is
+calculated directly from the schedule's origin and the interval ordinal by
+multiplying each ISO 8601 duration component by the ordinal and applying
+years, months, days, hours, minutes, then seconds.
+
+* Origins: ``utc`` counts from 1970-01-01T00:00:00Z; ``account_timezone`` and
+  ``source_timezone`` from local midnight on 1970-01-01 in their zone;
+  ``billing_cycle`` from its explicit ``period_anchor`` expressed in its zone.
+* Years, months and days are local civil arithmetic in the zone. The day is
+  clamped from the origin's day (a March 31 anchor gives February 28, then
+  March 31 again). A nonexistent local time advances by the gap; an ambiguous
+  one takes the earlier instant.
+* Hours, minutes and seconds are exact elapsed time added after the civil part,
+  so ``PT24H`` differs from ``P1D`` across a DST change. The spec does not say
+  whether time components are civil; this matches the TypeScript SDK
+  (adcontextprotocol/adcp-client#3505), so both SDKs derive identical periods.
+* A zero-length period (a skipped civil date) is never a period.
+* Sub-daily local periods (adcp#8588): under ``account_timezone``,
+  ``source_timezone`` or ``billing_cycle`` alignment, a duration of hours,
+  minutes and seconds only MUST divide 24 hours, and its boundaries are the
+  instants whose local wall-clock time is a whole multiple of the duration
+  after local midnight, counted afresh each local day. A nonexistent wall time
+  yields no boundary and a repeated one yields one boundary per offset, so a
+  23-hour DST day has 23 hourly periods and a 25-hour day 25. Local durations
+  cannot mix date and time components.
+
+The ledger's ``ReportingScheduleSpec`` treats every component as civil time and
+defaults an anchorless civil schedule to the UTC epoch in local time; this
+calendar does neither.
+"""
+
+from __future__ import annotations
+
+import calendar as _calendar
+import re
+from collections.abc import Iterator
+from dataclasses import dataclass, field
+from datetime import date, datetime, time, timedelta, timezone
+from functools import lru_cache
+from zoneinfo import ZoneInfo, ZoneInfoNotFoundError, available_timezones
+
+UTC = timezone.utc
+_DURATION = re.compile(r"P(?:(\d+)Y)?(?:(\d+)M)?(?:(\d+)D)?(?:T(?:(\d+)H)?(?:(\d+)M)?(?:(\d+)S)?)?")
+_SLA = re.compile(r"P(?:(\d+)D)?(?:T(?:(\d+)H)?(?:(\d+)M)?(?:(\d+)S)?)?")
+
+
+def utc_instant(value: datetime, *, field: str = "timestamp") -> datetime:
+    """Return ``value`` in UTC, refusing naive datetimes."""
+    if value.tzinfo is None or value.utcoffset() is None:
+        raise ValueError(f"{field} must be timezone-aware")
+    return value.astimezone(UTC)
+
+
+@lru_cache(maxsize=1)
+def _iana_zones() -> frozenset[str]:
+    return frozenset(available_timezones())
+
+
+def require_zone(name: str | None, *, field: str = "timezone") -> ZoneInfo:
+    """A recognized IANA zone; numeric offsets, unknown names and keys that are
+    not IANA zone names (``posixrules``, ``right/UTC``, ``posix/...``) are refused."""
+    if not name or name[0] in "+-" or name[0].isdigit() or name not in _iana_zones():
+        raise ValueError(f"{field} {name!r} is not a recognized IANA timezone")
+    try:
+        return ZoneInfo(name)
+    except (ZoneInfoNotFoundError, ValueError) as error:
+        raise ValueError(f"{field} {name!r} is not a recognized IANA timezone") from error
+
+
+def parse_period_duration(value: str) -> tuple[int, int, int, int]:
+    """``(years, months, days, seconds)`` of a strictly positive duration."""
+    match = _DURATION.fullmatch(value)
+    if match is None or value in {"P", "PT"} or value.endswith("T"):
+        raise ValueError(f"{value!r} is not an ISO 8601 period duration")
+    years, months, days, hours, minutes, seconds = (int(item or 0) for item in match.groups())
+    exact = hours * 3600 + minutes * 60 + seconds
+    if not (years or months or days or exact):
+        raise ValueError("period_duration must be positive")
+    return years, months, days, exact
+
+
+def parse_delivery_sla(value: str) -> timedelta:
+    """A non-negative ``delivery_sla`` as exact elapsed time (days are 24 hours).
+
+    A ``delivery_sla`` with years or months, which the offering schema allows,
+    has no agreed arithmetic across SDKs and is refused.
+    """
+    match = _SLA.fullmatch(value)
+    if match is None or value in {"P", "PT"} or value.endswith("T"):
+        raise ValueError(
+            f"delivery_sla {value!r} is not supported: use days, hours, minutes and "
+            "seconds only (years and months have no agreed arithmetic)"
+        )
+    days, hours, minutes, seconds = (int(item or 0) for item in match.groups())
+    return timedelta(days=days, hours=hours, minutes=minutes, seconds=seconds)
+
+
+def _resolve(local: datetime, zone: ZoneInfo) -> datetime:
+    """Local civil time to an instant: a gap advances, a fold takes the earlier."""
+    return local.replace(tzinfo=zone, fold=0).astimezone(UTC)
+
+
+def _add_months(local: datetime, months: int, origin_day: int) -> datetime:
+    index = local.year * 12 + (local.month - 1) + months
+    year, month = divmod(index, 12)
+    month += 1
+    day = min(origin_day, _calendar.monthrange(year, month)[1])
+    return local.replace(year=year, month=month, day=day)
+
+
+@dataclass(frozen=True)
+class PeriodCalendar:
+    """Ordered half-open periods of one schedule in one zone."""
+
+    period_duration: str
+    zone_name: str
+    origin: datetime  # naive local civil time
+    delivery_sla: timedelta = timedelta(0)
+    #: Local alignment (anything but ``utc``): sub-daily durations restart at
+    #: each local midnight (adcp#8588).
+    local: bool = False
+    _parts: tuple[int, int, int, int] = field(init=False, repr=False, compare=False)
+    _zone: ZoneInfo = field(init=False, repr=False, compare=False)
+    _approx: float = field(init=False, repr=False, compare=False)
+
+    def __post_init__(self) -> None:
+        parts = parse_period_duration(self.period_duration)
+        object.__setattr__(self, "_parts", parts)
+        object.__setattr__(self, "_zone", require_zone(self.zone_name))
+        if self.origin.tzinfo is not None:
+            raise ValueError("origin is local civil time and must be naive")
+        years, months, days, exact = parts
+        if self.local and exact and (years or months or days):
+            raise ValueError(
+                f"period_duration {self.period_duration!r} mixes date and time components, "
+                "which a local alignment does not allow"
+            )
+        if self.local and exact and not (years or months or days) and 86400 % exact:
+            raise ValueError(
+                f"period_duration {self.period_duration!r} must divide 24 hours "
+                "under a local alignment"
+            )
+        approx = years * 365.2425 * 86400 + months * 30.436875 * 86400 + days * 86400 + exact
+        object.__setattr__(self, "_approx", approx)
+
+    @classmethod
+    def for_schedule(
+        cls,
+        *,
+        period_duration: str,
+        delivery_sla: str,
+        zone_name: str,
+        anchor: datetime | None = None,
+        local: bool = False,
+    ) -> PeriodCalendar:
+        """``anchor`` is an instant (``billing_cycle``); otherwise local midnight 1970-01-01.
+
+        ``local`` marks an ``account_timezone``, ``source_timezone`` or
+        ``billing_cycle`` schedule.
+        """
+        zone = require_zone(zone_name)
+        origin = (
+            utc_instant(anchor, field="period_anchor").astimezone(zone).replace(tzinfo=None)
+            if anchor is not None
+            else datetime(1970, 1, 1)
+        )
+        return cls(
+            period_duration, zone_name, origin, parse_delivery_sla(delivery_sla), local=local
+        )
+
+    @property
+    def _subdaily_local(self) -> bool:
+        years, months, days, exact = self._parts
+        return self.local and bool(exact) and not (years or months or days)
+
+    def _day_boundaries(self, day: date) -> list[datetime]:
+        """Every boundary on one local date: wall-clock multiples after local midnight."""
+        step = self._parts[3]
+        found: set[datetime] = set()
+        midnight = datetime.combine(day, time())
+        for index in range(86400 // step):
+            wall = midnight + timedelta(seconds=index * step)
+            for fold in (0, 1):
+                instant = wall.replace(tzinfo=self._zone, fold=fold).astimezone(UTC)
+                if instant.astimezone(self._zone).replace(tzinfo=None) == wall:
+                    found.add(instant)
+        return sorted(found)
+
+    def _boundaries_from(self, instant: datetime) -> Iterator[datetime]:
+        """Sub-daily local boundaries at or after ``instant``, in order."""
+        at = utc_instant(instant)
+        day = at.astimezone(self._zone).date() - timedelta(days=1)
+        while True:
+            for boundary in self._day_boundaries(day):
+                if boundary >= at:
+                    yield boundary
+            day += timedelta(days=1)
+
+    def boundary(self, ordinal: int) -> datetime:
+        years, months, days, exact = self._parts
+        local = self.origin
+        if years or months:
+            local = _add_months(local, (years * 12 + months) * ordinal, self.origin.day)
+        if days:
+            local = local + timedelta(days=days * ordinal)
+        return _resolve(local, self._zone) + timedelta(seconds=exact * ordinal)
+
+    def bounds(self, ordinal: int) -> tuple[datetime, datetime]:
+        return self.boundary(ordinal), self.boundary(ordinal + 1)
+
+    def first_ordinal_at_or_after(self, instant: datetime) -> int:
+        at = utc_instant(instant)
+        origin = self.boundary(0)
+        ordinal = int((at - origin).total_seconds() // self._approx)
+        while self.boundary(ordinal) < at:
+            ordinal += 1
+        while self.boundary(ordinal - 1) >= at:
+            ordinal -= 1
+        return ordinal
+
+    def ceil(self, instant: datetime) -> datetime:
+        """The first boundary at or after ``instant`` (E for a cutover at it)."""
+        if self._subdaily_local:
+            return next(self._boundaries_from(instant))
+        return self.boundary(self.first_ordinal_at_or_after(instant))
+
+    def floor(self, instant: datetime) -> datetime:
+        """The last boundary at or before ``instant``."""
+        at = utc_instant(instant)
+        if self._subdaily_local:
+            day = at.astimezone(self._zone).date() + timedelta(days=1)
+            while True:
+                earlier = [item for item in self._day_boundaries(day) if item <= at]
+                if earlier:
+                    return earlier[-1]
+                day -= timedelta(days=1)
+        ordinal = self.first_ordinal_at_or_after(at)
+        start = self.boundary(ordinal)
+        return start if start == at else self.boundary(ordinal - 1)
+
+    def periods(
+        self, *, starts_from: datetime, starts_before: datetime
+    ) -> Iterator[tuple[datetime, datetime]]:
+        """Every nonempty period whose start lies in ``[starts_from, starts_before)``."""
+        upper = utc_instant(starts_before)
+        if self._subdaily_local:
+            boundaries = self._boundaries_from(starts_from)
+            start = next(boundaries)
+            while start < upper:
+                end = next(boundaries)
+                yield start, end
+                start = end
+            return
+        ordinal = self.first_ordinal_at_or_after(starts_from)
+        start = self.boundary(ordinal)
+        while start < upper:
+            end = self.boundary(ordinal + 1)
+            if end > start:
+                yield start, end
+            ordinal += 1
+            start = end
+
+
+def iso_z(value: datetime) -> str:
+    """RFC 3339 UTC with a ``Z`` suffix and no fractional seconds when whole."""
+    instant = utc_instant(value)
+    if instant.microsecond:
+        return instant.isoformat().replace("+00:00", "Z")
+    return instant.strftime("%Y-%m-%dT%H:%M:%SZ")
+
+
+__all__ = [
+    "PeriodCalendar",
+    "iso_z",
+    "parse_delivery_sla",
+    "parse_period_duration",
+    "require_zone",
+    "utc_instant",
+]
Original file line number	Diff line number	Diff line change
`@@ -161,6 +161,7 @@`
`161`	`161`	`"service",`
`162`	`162`	`"service_production",`
`163`	`163`	`"source",`
	`164`	`+ "subscriptions",`
`164`	`165`	`"testing",`
`165`	`166`	`}`
`166`	`167`	`)`