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Output "from Now" string in Kotlin using UTC timezone

I'm trying to write a Kotlin function which replicates the behaviour of fromNow in the moment library.
I have the following code:
fun formatDuration(dateTime: String): String {
try {
val parsedDateTime = Instant.parse(dateTime)
val prettyTime = PrettyTime()
prettyTime.reference = Instant.now().atZone(ZoneOffset.UTC).toInstant()
return prettyTime.format(parsedDateTime)
} catch (e: DateTimeParseException) {
e.printStackTrace()
return "Invalid date/time format"
}
}
The problem is when the device time is 9:44 and the input string is 2023-02-19T11:48:09.958Z, and the current UTC time is 15:19 it will output 2 hours from now, even though it should output 3 hours ago like the moment function does as the timestamp is in UTC.
How can I fix this to always take into account UTC time not local time when calculating the difference?

Have you tried to change:
from:
val parsedDateTime = Instant.parse(dateTime)
to:
val parsedDateTime = Instant.parse(dateTime).atZone(ZoneOffset.UTC).toInstant()

How to parse date "2022-07-18T08:24:18Z" in android

I have tried these format but none worked.
yyyy-MM-dd'T'HH:mm:ss'Z'
yyyy-MM-dd'T'HH:mm:ssZ
yyyy-MM-dd'T'HH:mm:ssZZ
yyyy-MM-dd'T'HH:mm:ss
Also tried "ZonedDateTime", but it is not available below Android O.

If your minSDK is 25 or lower you have to use Java 8+ API desugaring support to be able to use the java.time package from Java 8.
With that enabled you can simply use e.g.
OffsetDateTime.parse("2022-07-18T08:24:18Z")
ZonedDateTime.parse("2022-07-18T08:24:18Z")
(you can find many resources about the differences of these date formats).

You can do it like this
fun parseDate(
inputDateString: String?,
inputDateFormat: SimpleDateFormat,
outputDateFormat: SimpleDateFormat
): String? {
var date: Date? = null
var outputDateString: String? = null
try {
date = inputDateFormat.parse(inputDateString)
outputDateString = outputDateFormat.format(date)
} catch (e: ParseException) {
e.printStackTrace()
}
return outputDateString
}
inputString will be your Date, ex:"2022-07-18T08:24:18Z"
inputDateFormat : SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'",
Locale.US)
outputDateFormat : in whichever format you want to show the date
I hope you get your answer from this

Convert Date String to Date object in Kotlin? How to calculate number of days between today and specific date in Kotlin?

Part 1:
I have date as string in the following format: "2020-10-15T22:54:54Z"
I have to convert it into date object.
Tried the following:
val dateString = "2020-10-15T22:54:54Z"
val dateFormatter = DateTimeFormatter.ofPattern("%Y-%m-%dT%H:%M:%SZ")
val updatedAtDate = LocalDate.parse(dateString, dateFormatter)
val today = LocalDateTime.now()
println("Updated At: $updatedAtDate")
Gives the following error: "Unknown pattern letter: T"
Part 2:
Once I have the date object from above, I have to calculate the difference between today (Current Date) and the above date. How to do it in Kotlin?

tl;dr You don't need to create a custom formatter…
… for the val dateString = "2020-10-15T22:54:54Z" here, it is formatted in an ISO standard. Therefore, you can simply do this (if you want a LocalDate, just year, month and day):
val thatDate: LocalDate = OffsetDateTime.parse(dateString).toLocalDate()
Fully adressing all the aspects of your post:
You can utilize a java.time.Period.between(LocalDate, LocalDate) in order to calculate the difference between two LocalDates. You only have to make sure the older date is the first argument, otherwise you will get a negative result. Here's a full example:
import java.time.OffsetDateTime
import java.time.LocalDate
import java.time.Period
fun main(args: Array<String>) {
val dateString = "2020-10-15T22:54:54Z"
// create an OffsetDateTime directly
val thatDate = OffsetDateTime.parse(dateString)
// and extract the date
.toLocalDate()
// get the current day (date only!)
val today = LocalDate.now()
// calculate the difference in days and make sure to get a positive result
val difference = if (today.isBefore(thatDate))
Period.between(today, thatDate).days
else
Period.between(thatDate, today).days
// print something containing both dates and the difference
println("[$today] Updated At: $thatDate, difference: $difference days")
}
Output at Dec 10, 2021:
[2021-12-10] Updated At: 2020-10-15, difference: 25 days

How to put an outcome of a function in Kotlin into a Textview

I am quite new with programming in Kotlin in Android Studio.
I created a function and now I want to put the outcome of the function into a textview.
I am struggling with this for a couple of days now and I cant figure out how to do this. I used a function I found here on Stackoverflow of a welcome message based on time. It is the following function:
fun getGreetingMessage(): String {
val c = Calendar.getInstance()
val timeOfDay = c.get(Calendar.HOUR_OF_DAY)
return when (timeOfDay) {
in 0..11 -> "Good morning"
in 12..15 -> "Goede afternoon"
in 16..20 -> "Goede evening"
else -> "Hello"
The outcome of this function must be presented in a Textview on my main page can someone please help me out here?
many thanks,
Rick

Based on the question you asked the problem is assigning data to TextView.
now let`s say the id of TextView is some_id
the code should look something like this.
//getting data from getGreetingMessageFunction
val greetingMessage = getGreetingMessage()
//declaring the view
val requiredView = view.findViewId<TextView>(R.id.some_id)
//assigning the greeting message to the required view
requiredView.text=greetingMessage
fun getGreetingMessage(): String {
val c = Calendar.getInstance()
val timeOfDay = c.get(Calendar.HOUR_OF_DAY)
return when (timeOfDay) {
in 0..11 -> "Good morning"
in 12..15 -> "Goede afternoon"
in 16..20 -> "Goede evening"
else -> "Hello"
}
}

App level kotlin function in android project

Can anybody explain how I can release an app-level kotlin function in Android Studio project? I have an Android application and I try do someting like this:
var date: Date = Date()
/////////////////////////////////////////////////////////
// this block must be app-level fun
val format = “dd.MM.yyyy”
val simpleDateFormat = SimpleDateFormat(format)
var formattedDate = simpleDateFormat.format(date)
/////////////////////////////////////////////////////////
convert Date object to String with custom format. I do it many times (in different activities and fragments) in my project, so I think it will be good idea to releas this code as function (or class, if it will be more efficient). Thus I have date and format as input parameters and formattedDate as output. Also it will be good to set default format value

You can create an extension function on Date that accepts a format and uses it to convert the date to that format. You can also define the default format on the input parameter. Something like:
fun Date.toFormattedString(format: String = "dd.MM.yyyy"): String {
val simpleDateFormat = SimpleDateFormat(format)
return simpleDateFormat.format(this)
}
Place it in a file where the whole app can access it (e.g., a file named Extensions.kt in a module/package where you put all reusable and/or helper code) and then just use the function like someDate.toFormattedString().

Here is an example of my function contained in separate kotlin file called Time.kt
fun timeConverter(string: String?, i: Int): String {
val isoFormat = "yyyy-MM-dd'T'HH:mm:ss"
var expectedFormat = "dd/MM"
when(i){
0 -> expectedFormat = "dd/MM"
1 -> expectedFormat = "EEE"
2 -> expectedFormat = "HH:mm"
3 -> expectedFormat = "EEE, dd/MM"
}
val dateFormat = SimpleDateFormat(isoFormat, Locale.getDefault())
val date = dateFormat.parse(string)
return SimpleDateFormat(expectedFormat).format(date)
}

Make the function part of an object.
https://www.baeldung.com/kotlin-objects
Objects (not class) in Kotlin are static. If you import the object from where you use the function, it can be used anywhere without being instantiated.

You can have a DateUtil class that holds a format function as companion. You will be able to use it anywhere in your app without instantiating it.
class DateUtil{
companion object {
fun format(date: Date):String{
val format = "dd.MM.yyyy"
val simpleDateFormat = SimpleDateFormat(format)
return simpleDateFormat.format(date)
}
}
}
Then you call it: DateUtil.format(Date())