perf(core): avoid Calendar allocations in the device date provider

.changeset/chilly-tools-like.md

@@ -0,0 +1,9 @@
+---
+"posthog": patch
+"posthog-android": patch
+"posthog-server": patch
+"posthog-android-surveys-compose": patch
+"posthog-server-openfeature": patch
+---
+
+Avoid unnecessary Calendar allocations when reading device-clock timestamps.

posthog/src/main/java/com/posthog/internal/PostHogDeviceDateProvider.kt

@@ -1,7 +1,6 @@
 package com.posthog.internal
 
 import com.posthog.PostHogInternal
-import java.util.Calendar
 import java.util.Date
 
 /**
@@ -11,14 +10,11 @@ import java.util.Date
 @PostHogInternal
 public class PostHogDeviceDateProvider : PostHogDateProvider {
     override fun currentDate(): Date {
-        val cal = Calendar.getInstance()
-        return cal.time
+        return Date()
     }
 
     override fun addSecondsToCurrentDate(seconds: Int): Date {
-        val cal = Calendar.getInstance()
-        cal.add(Calendar.SECOND, seconds)
-        return cal.time
+        return Date(System.currentTimeMillis() + seconds * 1000L)
     }
 
     override fun currentTimeMillis(): Long {

posthog/src/test/java/com/posthog/internal/PostHogDeviceDateProviderTest.kt

@@ -0,0 +1,29 @@
+package com.posthog.internal
+
+import kotlin.test.Test
+import kotlin.test.assertTrue
+
+internal class PostHogDeviceDateProviderTest {
+    private val provider = PostHogDeviceDateProvider()
+
+    @Test
+    fun `current date uses the wall clock`() {
+        val before = System.currentTimeMillis()
+        val actual = provider.currentDate().time
+        val after = System.currentTimeMillis()
+
+        assertTrue(actual in before..after)
+    }
+
+    @Test
+    fun `adding seconds uses elapsed milliseconds without integer overflow`() {
+        listOf(Int.MIN_VALUE, -3601, 0, 3601, Int.MAX_VALUE).forEach { seconds ->
+            val offset = seconds * 1000L
+            val before = System.currentTimeMillis() + offset
+            val actual = provider.addSecondsToCurrentDate(seconds).time
+            val after = System.currentTimeMillis() + offset
+
+            assertTrue(actual in before..after, "Unexpected date for $seconds seconds: $actual")
+        }
+    }
+}