diff --git a/core/src/main/java/com/amplitude/core/utilities/HttpClient.kt b/core/src/main/java/com/amplitude/core/utilities/HttpClient.kt
index eecb0ea0..a7b977c4 100644
--- a/core/src/main/java/com/amplitude/core/utilities/HttpClient.kt
+++ b/core/src/main/java/com/amplitude/core/utilities/HttpClient.kt
@@ -85,7 +85,7 @@ internal class HttpClient(
     }
 
     internal fun getClientUploadTime(): String {
-        val currentTimeMillis = System.currentTimeMillis()
+        val currentTimeMillis = getCurrentTimeMillis()
         val sdf = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'")
         sdf.timeZone = TimeZone.getTimeZone("UTC")
         return sdf.format(Date(currentTimeMillis))
@@ -95,6 +95,10 @@ internal class HttpClient(
         return configuration.minIdLength
     }
 
+    internal fun getCurrentTimeMillis(): Long {
+        return System.currentTimeMillis()
+    }
+
     fun getInputStream(connection: HttpURLConnection): InputStream {
         return try {
             connection.inputStream
@@ -149,7 +153,7 @@ abstract class Connection(
         if (minIdLength == null) {
             return "{\"api_key\":\"$apiKey\",\"client_upload_time\":\"$clientUploadTime\",\"events\":$events}"
         }
-        return "{\"api_key\":\"$apiKey\",\"client_upload_time\":$clientUploadTime,\"events\":$events,\"options\":{\"min_id_length\":$minIdLength}}"
+        return "{\"api_key\":\"$apiKey\",\"client_upload_time\":\"$clientUploadTime\",\"events\":$events,\"options\":{\"min_id_length\":$minIdLength}}"
     }
 }
 
diff --git a/core/src/test/kotlin/com/amplitude/core/utilities/HttpClientTest.kt b/core/src/test/kotlin/com/amplitude/core/utilities/HttpClientTest.kt
new file mode 100644
index 00000000..191bf1a5
--- /dev/null
+++ b/core/src/test/kotlin/com/amplitude/core/utilities/HttpClientTest.kt
@@ -0,0 +1,102 @@
+package com.amplitude.core.utilities
+
+import com.amplitude.core.Configuration
+import com.amplitude.core.events.BaseEvent
+import io.mockk.every
+import io.mockk.spyk
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import okhttp3.mockwebserver.MockResponse
+import okhttp3.mockwebserver.MockWebServer
+import okhttp3.mockwebserver.RecordedRequest
+import org.json.JSONObject
+import org.junit.jupiter.api.AfterEach
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.TestInstance
+import java.util.concurrent.TimeUnit
+
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+class HttpClientTest {
+    private lateinit var server: MockWebServer
+    val apiKey = "API_KEY"
+    val clientUploadTimeMillis = 1699905773000L
+    val clientUploadTimeString = "2023-11-13T20:02:53.000Z"
+
+    @ExperimentalCoroutinesApi
+    @BeforeEach
+    fun setup() {
+        server = MockWebServer()
+        server.start()
+    }
+
+    @AfterEach
+    fun shutdown() {
+        server.shutdown()
+    }
+
+    @Test
+    fun `test client_upload_time is set on the request`() {
+        server.enqueue(MockResponse().setBody("{\"code\": \"success\"}"))
+
+        val config = Configuration(
+            apiKey = apiKey,
+            serverUrl = server.url("/").toString()
+        )
+        val event = BaseEvent()
+        event.eventType = "test"
+
+        val httpClient = spyk(HttpClient(config))
+        every { httpClient.getCurrentTimeMillis() } returns clientUploadTimeMillis
+
+        val connection = httpClient.upload()
+        connection.outputStream?.let {
+            connection.setEvents(JSONUtil.eventsToString(listOf(event)))
+            // Upload the payloads.
+            connection.close()
+        }
+
+        val request = runRequest()
+        val result = JSONObject(request?.body?.readUtf8())
+
+        assertEquals(apiKey, result.getString("api_key"))
+        assertEquals(clientUploadTimeString, result.getString("client_upload_time"))
+    }
+
+    @Test
+    fun `test client_upload_time is set correctly when minIdLength is set`() {
+        server.enqueue(MockResponse().setBody("{\"code\": \"success\"}"))
+
+        val config = Configuration(
+            apiKey = apiKey,
+            serverUrl = server.url("/").toString(),
+            minIdLength = 3,
+        )
+        val event = BaseEvent()
+        event.eventType = "test"
+
+        val httpClient = spyk(HttpClient(config))
+        every { httpClient.getCurrentTimeMillis() } returns clientUploadTimeMillis
+
+        val connection = httpClient.upload()
+        connection.outputStream?.let {
+            connection.setEvents(JSONUtil.eventsToString(listOf(event)))
+            // Upload the payloads.
+            connection.close()
+        }
+
+        val request = runRequest()
+        val result = JSONObject(request?.body?.readUtf8())
+
+        assertEquals(apiKey, result.getString("api_key"))
+        assertEquals(clientUploadTimeString, result.getString("client_upload_time"))
+    }
+
+    private fun runRequest(): RecordedRequest? {
+        return try {
+            server.takeRequest(5, TimeUnit.SECONDS)
+        } catch (e: InterruptedException) {
+            null
+        }
+    }
+}