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diff --git a/src/jet/utils/app-event-formatted-date.ts b/src/jet/utils/app-event-formatted-date.ts
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+++ b/src/jet/utils/app-event-formatted-date.ts
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+import {
+    type Optional,
+    isSome,
+    isNothing,
+} from '@jet/environment/types/optional';
+import type { LocalizationWrapper } from '@jet-app/app-store/foundation/wrappers/localization';
+import type {
+    AppEventFormattedDate,
+    AppEventBadgeKind,
+} from '@jet-app/app-store/api/models';
+import type { AppStoreObjectGraph } from '@jet-app/app-store/foundation/runtime/app-store-object-graph';
+import { formattedDatesWithKind } from '@jet-app/app-store/common/app-promotions/app-event';
+
+/**
+ * Partial type of {@linkcode AppEventFormattedDate} with just the properties
+ * that are actually used
+ */
+export type RequiredAppEventFormattedDate = Pick<
+    AppEventFormattedDate,
+    'displayText' | 'displayFromDate' | 'countdownToDate' | 'countdownStringKey'
+>;
+
+/**
+ * Represents a client-side serialization of an {@linkcode RequiredAppEventFormattedDate}
+ *
+ * This is needed because our client-side code will receive the event object with `Date` properties
+ * serialized as ISO 8601-formatted strings, while the server-side code will receive the original
+ * `Date` values. We need to normalize this to make sure we have consistent logic in both environments
+ */
+type SerializedAppEventFormattedDate = Pick<
+    RequiredAppEventFormattedDate,
+    'displayText' | 'countdownStringKey'
+> & {
+    readonly displayFromDate?: string;
+    readonly countdownToDate?: string;
+};
+
+function deserializeDate(value: Optional<Date | string>): Date | undefined {
+    if (isNothing(value)) {
+        return undefined;
+    }
+
+    return typeof value === 'string' ? new Date(value) : value;
+}
+
+/**
+ * Turn {@linkcode date} in either the client- or server-side format into the
+ * server-side format by parsing the ISO 8601 string values into `Date` instances
+ */
+function deserializeDateProperties(
+    date: SerializedAppEventFormattedDate | RequiredAppEventFormattedDate,
+): RequiredAppEventFormattedDate {
+    const { countdownToDate, displayFromDate, ...rest } = date;
+
+    return {
+        // Normalize properties that might have been serialized as `string` to `Date`
+        countdownToDate: deserializeDate(countdownToDate),
+        displayFromDate: deserializeDate(displayFromDate),
+
+        // Use all of the other properties with their existing values
+        ...rest,
+    };
+}
+
+/**
+ * A {@linkcode RequiredAppEventFormattedDate} with a definitely-defined `.displayFromDate` property
+ */
+type AppEventFormattedDateWithDisplayFromDate =
+    RequiredAppEventFormattedDate & {
+        readonly displayFromDate: Date;
+    };
+
+function hasDisplayRequirement(
+    date: RequiredAppEventFormattedDate,
+): date is AppEventFormattedDateWithDisplayFromDate {
+    return isSome(date.displayFromDate);
+}
+
+export function chooseAppEventDate(
+    dates: (SerializedAppEventFormattedDate | RequiredAppEventFormattedDate)[],
+): Optional<RequiredAppEventFormattedDate> {
+    const nowTime = Date.now();
+
+    // We might be passed `dates` in the expected format (server-side) or with their `Date`
+    // properties serialized as strings (client-side); we need to normalize them all to the
+    // same format
+    const normalizedDates = dates.map((date) =>
+        deserializeDateProperties(date),
+    );
+
+    // A `dates` member might not have a `.displayFromDate`; if that's the case, we will
+    // use that as a fallback if all other options are in the future
+    const fallback = normalizedDates.find(
+        (date) => !hasDisplayRequirement(date),
+    );
+
+    // Find all of the `dates` members with a `.displayFromDate` in the past
+    const optionsWithPastDisplayFromDates = normalizedDates
+        // Ensure all `date` objects have a display requirement
+        .filter((date) => hasDisplayRequirement(date))
+        // Filter out any `date` objects with a display requirement in the future
+        .filter((date) => {
+            const dateTime = date.displayFromDate.getTime();
+            const timeDifference = nowTime - dateTime;
+
+            return timeDifference > 0;
+        });
+
+    // If there are none, use the fallback
+    if (optionsWithPastDisplayFromDates.length === 0) {
+        return fallback;
+    }
+
+    // Otherwise, find the `date` object with the most recent `.displayFromDate`
+    return optionsWithPastDisplayFromDates.reduce((acc, next) => {
+        const accTime = acc.displayFromDate.getTime();
+        const nextTime = next.displayFromDate.getTime();
+
+        // Which time is closer to "now"?
+        const accTimeDiff = nowTime - accTime;
+        const nextTimeDiff = nowTime - nextTime;
+
+        return accTimeDiff > nextTimeDiff ? next : acc;
+    });
+}
+
+/**
+ * Partial type of {@linkcode LocalizationWrapper} with just the methods that
+ * are actually called
+ *
+ * This partial type simplifies testing by reducing the surface area of the function's
+ * dependencies
+ */
+type RequiredLocalization = Pick<LocalizationWrapper, 'string'>;
+
+function msToMinutes(ms: number): number {
+    return ms / (1_000 * 60);
+}
+
+export function renderDate(
+    localization: RequiredLocalization,
+    date: RequiredAppEventFormattedDate,
+): Optional<string> {
+    if (typeof date.countdownStringKey === 'string' && date.countdownToDate) {
+        const nowTime = Date.now();
+        const translationString = localization.string(date.countdownStringKey);
+
+        const countdownToDateTime = date.countdownToDate.getTime();
+        const diffTime = countdownToDateTime - nowTime;
+
+        const count = Math.floor(msToMinutes(diffTime));
+
+        return translationString.replace('@@count@@', count.toString());
+    }
+
+    if (typeof date.displayText === 'string') {
+        return date.displayText;
+    }
+
+    return undefined;
+}
+
+/**
+ * Helper function to compute formatted dates for app events.
+ * Handles date conversion and error handling.
+ *
+ * @param objectGraph - objectGraph from Jet
+ * @param badgeKind - The badge kind from the app event
+ * @param startDate - The start date (string or Date)
+ * @param endDate - The optional end date (string or Date)
+ * @returns Array of formatted dates or undefined if an error occurs
+ */
+export function computeAppEventFormattedDates(
+    objectGraph: AppStoreObjectGraph,
+    badgeKind: AppEventBadgeKind,
+    startDate: string | Date,
+    endDate?: string | Date | null,
+): RequiredAppEventFormattedDate[] | undefined {
+    // Use deserializeDate function to convert dates
+    const startDateObj = deserializeDate(startDate);
+    const endDateObj = deserializeDate(endDate);
+
+    // Validate that we have a valid start date
+    if (!startDateObj || isNaN(startDateObj.getTime())) {
+        return undefined;
+    }
+
+    return formattedDatesWithKind(
+        objectGraph,
+        badgeKind,
+        startDateObj,
+        endDateObj,
+    );
+}