Match UTC timezone logic in JVM code

uhabits-core/src/commonMain/kotlin/org/isoron/platform/time/Dates.kt

@@ -25,6 +25,7 @@ import kotlinx.datetime.Instant
 import kotlinx.datetime.LocalDateTime
 import kotlinx.datetime.Month
 import kotlinx.datetime.TimeZone
+import kotlinx.datetime.TimeZone.Companion.UTC
 import kotlinx.datetime.offsetAt
 import kotlinx.datetime.toInstant
 import kotlinx.datetime.toLocalDateTime
@@ -265,7 +266,7 @@ data class LocalDate(val daysSince2000: Int) {
                     minute = minute,
                     second = 0
                 ).toInstant(
-                    getTimeZone()
+                    UTC
                 ).toEpochMilliseconds()
 
             if (getLocalTime() > time) {

uhabits-core/src/commonTest/kotlin/org/isoron/platform/time/DatesTest.kt

@@ -420,7 +420,7 @@ class DatesTest : BaseUnitTest() {
     fun testGetUpcomingTimeInMillis_withTimeZone() {
         LocalDate.fixedLocalTime = FIXED_LOCAL_TIME
         LocalDate.fixedTimeZone = TimeZone.of("GMT-$HOUR_OFFSET")
-        val expected = unixTime(2015, Month.JANUARY, 25, 10, 1)
+        val expected = unixTime(2015, Month.JANUARY, 25, 13, 1)
         val upcomingTimeMillis = getUpcomingTimeInMillis(10, 1)
         assertEquals(expected, upcomingTimeMillis)
     }