Add getLastRealtimeFetchTimestamp method

README.md

@@ -727,6 +727,15 @@ await gtfs.fetchRealtimeData(['./path/to/feed.pb']);
 // Update configuration
 gtfs.setRealtimeFeedUrls(['https://example.com/new-feed']);
 gtfs.setStalenessThreshold(60); // 60 seconds
+
+// Check when realtime data was last fetched
+const lastFetch = gtfs.getLastRealtimeFetchTimestamp();
+if (lastFetch) {
+  const ageSeconds = Math.floor(Date.now() / 1000) - lastFetch;
+  console.log(`RT data is ${ageSeconds} seconds old`);
+} else {
+  console.log('No RT data has been fetched yet');
+}
 ```
 
 #### Querying Alerts
@@ -1164,6 +1173,7 @@ All methods support flexible filtering with both single values and arrays:
 - `getRealtimeFeedUrls()` - Get configured RT feed URLs
 - `setStalenessThreshold(seconds)` - Set staleness threshold (default: 120 seconds)
 - `getStalenessThreshold()` - Get current staleness threshold
+- `getLastRealtimeFetchTimestamp()` - Get Unix timestamp (seconds) of last successful RT fetch, or null if never fetched
 - `getAlerts(filters?)` - Get alerts (filters: alertId, routeId, stopId, tripId, activeOnly, cause, effect, limit)
 - `getVehiclePositions(filters?)` - Get vehicle positions (filters: tripId, routeId, vehicleId, limit)
 - `getTripUpdates(filters?)` - Get trip updates (filters: tripId, routeId, limit)

src/gtfs-sqljs.ts

@@ -142,6 +142,7 @@ export class GtfsSqlJs {
   private SQL: SqlJsStatic | null = null;
   private realtimeFeedUrls: string[] = [];
   private stalenessThreshold: number = 120;
+  private lastRealtimeFetchTimestamp: number | null = null;
 
   /**
    * Private constructor - use static factory methods instead
@@ -875,6 +876,14 @@ export class GtfsSqlJs {
     return this.stalenessThreshold;
   }
 
+  /**
+   * Get timestamp of the last successful realtime data fetch and insertion
+   * @returns Unix timestamp in seconds, or null if no realtime data has been fetched
+   */
+  getLastRealtimeFetchTimestamp(): number | null {
+    return this.lastRealtimeFetchTimestamp;
+  }
+
   /**
    * Fetch and load GTFS Realtime data from configured feed URLs or provided URLs
    * @param urls - Optional array of feed URLs. If not provided, uses configured feed URLs
@@ -888,6 +897,7 @@ export class GtfsSqlJs {
     }
 
     await loadRealtimeData(this.db, feedUrls);
+    this.lastRealtimeFetchTimestamp = Math.floor(Date.now() / 1000);
   }
 
   /**