fix(train): the Loop set up, its clock in UTC as Polar's SDK parses it

doFirstTimeUse (SDK 8.3.0) parses the device time as
yyyy-MM-dd'T'HH:mm:ss'Z' and refused the offset and fractions of a second
the app sent (ISO_OFFSET_DATE_TIME), so no band was ever set up: "The band
didn't answer". The test's clock had neither; it has both now, and checks the
time against the SDK's pattern.

What fails in the Loop's bridge is logged now (tag Loop), as the app says
only that the band didn't answer.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/train/halkyon_train_flutter/android/app/src/main/kotlin/app/halkyon/train/LoopBridge.kt

@@ -1,6 +1,7 @@
 package app.halkyon.train
 
 import android.content.Context
+import android.util.Log
 import com.polar.androidcommunications.api.ble.model.DisInfo
 import com.polar.androidcommunications.api.ble.model.gatt.client.ChargeState
 import com.polar.androidcommunications.api.ble.model.gatt.client.PowerSourcesState
@@ -77,6 +78,7 @@ class LoopBridge(private val context: Context) : MethodChannel.MethodCallHandler
             } catch (error: SecurityException) {
               sink.error("refused", error.message, null)
             } catch (error: Exception) {
+              Log.w("Loop", "The search failed", error)
               sink.error("failed", error.message, null)
             }
           }
@@ -161,6 +163,8 @@ class LoopBridge(private val context: Context) : MethodChannel.MethodCallHandler
       } catch (error: SecurityException) {
         result.error("refused", error.message, null)
       } catch (error: Exception) {
+        // The app says only that the band didn't answer; what failed is here.
+        Log.w("Loop", "${call.method} failed", error)
         result.error("failed", error.message, null)
       }
     }

apps/train/halkyon_train_flutter/android/app/src/main/kotlin/app/halkyon/train/LoopSetup.kt

@@ -2,8 +2,10 @@ package app.halkyon.train
 
 import com.polar.sdk.api.model.PolarFirstTimeUseConfig
 import java.time.LocalDate
+import java.time.ZoneOffset
 import java.time.ZonedDateTime
 import java.time.format.DateTimeFormatter
+import java.util.Locale
 
 /**
  * The app's figures for a Loop's first-time use (ADR 0030, D34) as Polar's
@@ -22,6 +24,9 @@ object LoopSetup {
       "pro" to 60,
     )
 
+  /** The device time as Polar's SDK reads it. */
+  private val deviceTimeFormat = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.ENGLISH)
+
   /** Whether a device found under [name] is a Loop. */
   fun isLoop(name: String?): Boolean = name != null && name.trim().startsWith("Polar Loop", ignoreCase = true)
 
@@ -43,7 +48,9 @@ object LoopSetup {
       restingHeartRate = number("restingHeartRate").toInt(),
       trainingBackground =
         trainingBackgrounds[figures["trainingBackground"]] ?: throw IllegalArgumentException("trainingBackground missing"),
-      deviceTime = now.format(DateTimeFormatter.ISO_OFFSET_DATE_TIME),
+      // UTC to the second: doFirstTimeUse parses it as yyyy-MM-dd'T'HH:mm:ss'Z'
+      // (SDK 8.3.0), refusing an offset and fractions of a second.
+      deviceTime = now.withZoneSameInstant(ZoneOffset.UTC).format(deviceTimeFormat),
       typicalDay =
         when (figures["typicalDay"]) {
           "mostlySitting" -> PolarFirstTimeUseConfig.TypicalDay.MOSTLY_SITTING

apps/train/halkyon_train_flutter/android/app/src/test/kotlin/app/halkyon/train/LoopSetupTest.kt

@@ -2,8 +2,11 @@ package app.halkyon.train
 
 import com.polar.sdk.api.model.PolarFirstTimeUseConfig
 import java.time.LocalDate
+import java.time.LocalDateTime
 import java.time.ZoneOffset
 import java.time.ZonedDateTime
+import java.time.format.DateTimeFormatter
+import java.util.Locale
 import org.junit.Assert.assertEquals
 import org.junit.Assert.assertFalse
 import org.junit.Assert.assertThrows
@@ -13,7 +16,8 @@ import org.junit.Test
 // A Loop's first-time use from the app's figures (ADR 0030, D34): Polar's
 // names for the app's, and nothing sent that the SDK would refuse.
 class LoopSetupTest {
-  private val now = ZonedDateTime.of(2026, 10, 28, 18, 30, 0, 0, ZoneOffset.ofHours(1))
+  // Fractions of a second and an offset, as the phone's clock gives them.
+  private val now = ZonedDateTime.of(2026, 10, 28, 18, 30, 0, 792_484_000, ZoneOffset.ofHours(1))
 
   private val figures =
     mapOf<String, Any?>(
@@ -43,7 +47,10 @@ class LoopSetupTest {
     assertEquals(50, config.trainingBackground)
     assertEquals(PolarFirstTimeUseConfig.TypicalDay.MOSTLY_STANDING, config.typicalDay)
     assertEquals(480, config.sleepGoalMinutes)
-    assertEquals("2026-10-28T18:30:00+01:00", config.deviceTime)
+    // UTC to the second, as doFirstTimeUse parses it (SDK 8.3.0): it refused
+    // the offset and the fractions, and v0.1.0 never set a band up.
+    assertEquals("2026-10-28T17:30:00Z", config.deviceTime)
+    LocalDateTime.parse(config.deviceTime, DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.ENGLISH))
   }
 
   @Test