When submitting a new transaction, treat the chain as "synced" if the latest block is less than 30 minutes old. Increased from around 7.5 minutes.

src/main/java/org/qortal/api/resource/TransactionsResource.java

@@ -638,7 +638,10 @@ public class TransactionsResource {
 		ApiError.BLOCKCHAIN_NEEDS_SYNC, ApiError.INVALID_SIGNATURE, ApiError.INVALID_DATA, ApiError.TRANSFORMATION_ERROR, ApiError.REPOSITORY_ISSUE
 	})
 	public String processTransaction(String rawBytes58) {
-		if (!Controller.getInstance().isUpToDate())
+		// Only allow a transaction to be processed if our latest block is less than 30 minutes old
+		// If older than this, we should first wait until the blockchain is synced
+		final Long minLatestBlockTimestamp = NTP.getTime() - (30 * 60 * 1000L);
+		if (!Controller.getInstance().isUpToDate(minLatestBlockTimestamp))
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.BLOCKCHAIN_NEEDS_SYNC);
 
 		byte[] rawBytes = Base58.decode(rawBytes58);

src/main/java/org/qortal/controller/Controller.java

@@ -2048,10 +2048,13 @@ public class Controller extends Thread {
 		return peers;
 	}
 
-	/** Returns whether we think our node has up-to-date blockchain based on our info about other peers. */
+	/**
-	public boolean isUpToDate() {
+	 * Returns whether we think our node has up-to-date blockchain based on our info about other peers.
+	 * @param minLatestBlockTimestamp - the minimum block timestamp to be considered recent
+	 * @return boolean - whether our node's blockchain is up to date or not
+	 */
+	public boolean isUpToDate(Long minLatestBlockTimestamp) {
 		// Do we even have a vaguely recent block?
-		final Long minLatestBlockTimestamp = getMinimumLatestBlockTimestamp();
 		if (minLatestBlockTimestamp == null)
 			return false;
 
@@ -2077,6 +2080,16 @@ public class Controller extends Thread {
 		return !peers.isEmpty();
 	}
 
+	/**
+	 * Returns whether we think our node has up-to-date blockchain based on our info about other peers.
+	 * Uses the default minLatestBlockTimestamp value.
+	 * @return boolean - whether our node's blockchain is up to date or not
+	 */
+	public boolean isUpToDate() {
+		final Long minLatestBlockTimestamp = getMinimumLatestBlockTimestamp();
+		return this.isUpToDate(minLatestBlockTimestamp);
+	}
+
 	/** Returns minimum block timestamp for block to be considered 'recent', or <tt>null</tt> if NTP not synced. */
 	public static Long getMinimumLatestBlockTimestamp() {
 		Long now = NTP.getTime();