Session time is incorrect due to Time Zone change.

Overview (Required)

The reproduction procedure is as follows.

1. Visit Settings app. 1-1) Data & time > Set Time zone to London. (GMT+00:00) 1-2) Perform CLEAR DATA of droidkaigi2018 app.
2. Launch droidkaigi2018 app. (Sessions will be displayed soon.)
3. Finish app. (Back button)
4. Visit Settings app. 4-1) Data & time > Set Time zone to Tokyo. (GMT+09:00)
5. Launch droidkaigi2018 app. (The time of the displayed session is incorrect.)

As an impression that I read the code, the following code has doubts.

LocalDateTimeAdapter.kt

private val FORMATTER: DateTimeFormatter =
        DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss")
fun parseDateString(dateString: String?): LocalDateTime =
        LocalDateTime.parse(dateString, FORMATTER)

I guess that the time obtained from the server is based on Japan time. However, the application is parsing according to current Time Zone set for the terminal?

Links

[nukka123]

@takahirom

Ok. I send PR! #371

[nukka123]

@takahirom

I will introduce the code that I was verifying locally.

It is necessary to assume that the time expressed by LocalDateTime is JST.

fun LocalDateTime.toUnixMills(): Long = atZone(ZoneId.of("JST", ZoneId.SHORT_IDS))
        .toInstant().toEpochMilli()

    fun fromTimestamp(value: Long?): LocalDateTime? {
        if (value == null) {
            return null
        }
        return LocalDateTime.ofInstant(
                Instant.ofEpochSecond(value), ZoneId.of("JST", ZoneId.SHORT_IDS))
    }

Also, we should write javadoc about the time zone assumed by LocalDateTime.