diff --git a/src/Utils.php b/src/Utils.php
index d9bec28..d885c80 100644
--- a/src/Utils.php
+++ b/src/Utils.php
@@ -38,7 +38,7 @@ public static function transformCurrencies(array $currencies): array
 	public static function countTTL(DateTime $dateTime, int $beforeExpiration = 900): int
 	{
 		$time = time();
-		if (($dateTime->getTimestamp() - $beforeExpiration) < $time) {
+		if (($dateTime->getTimestamp() - $beforeExpiration) <= $time) {
 			$dateTime->modify('+1 day');
 		}
 
diff --git a/tests/src/UtilsTest.php b/tests/src/UtilsTest.php
new file mode 100644
index 0000000..71d1fe5
--- /dev/null
+++ b/tests/src/UtilsTest.php
@@ -0,0 +1,62 @@
+<?php
+
+declare(strict_types=1);
+
+namespace h4kuna\Exchange\Tests;
+
+use Closure;
+use DateTime;
+use h4kuna\Exchange\Utils;
+use Tester\Assert;
+use Tester\TestCase;
+
+require __DIR__ . '/../bootstrap.php';
+
+final class UtilsTest extends TestCase
+{
+	/**
+	 * @return array<string|int, array{0: Closure(static):void}>
+	 */
+	public function data(): array
+	{
+		return [
+			[
+				function (self $self) {
+					$self->assert(
+						901,
+						new DateTime('+901 seconds'),
+					);
+				},
+			],
+			[
+				function (self $self) {
+					$self->assert(
+						87300,
+						new DateTime('+900 seconds'),
+					);
+				},
+			],
+		];
+	}
+
+
+	/**
+	 * @param Closure(static):void $assert
+	 * @dataProvider data
+	 */
+	public function testCountTTL(Closure $assert): void
+	{
+		$assert($this);
+	}
+
+
+	public function assert(
+		int $expectedTime,
+		DateTime $from
+	): void
+	{
+		Assert::same($expectedTime, Utils::countTTL($from));
+	}
+}
+
+(new UtilsTest())->run();