如何将Flutter的TimeOfDay转换为DateTime并转为毫秒时间戳存储？

Got it, let's walk through how to turn that TimeOfDay from your picker into a timestamp integer you can store in your database. The key here is that TimeOfDay only holds hours and minutes—so we need to pair it with a date to create a full DateTime object first.

Step 1: Combine TimeOfDay with a Date #

Since TimeOfDay doesn’t include date information, you’ll want to attach it to a specific date. Most often, this is the current date (if you’re dealing with "today at X time"), but you could also use a user-selected date if you have a date picker paired with it.

Here’s how to do it with the current date:

// Your TimeOfDay from the picker
TimeOfDay selectedTime = _timePickerResult; 

// Grab the current date
DateTime currentDate = DateTime.now();

// Build a full DateTime using the current date + selected time
DateTime combinedDateTime = DateTime(
  currentDate.year,
  currentDate.month,
  currentDate.day,
  selectedTime.hour,
  selectedTime.minute,
);

If you’re working with a user-selected date (e.g., from a date picker), just replace currentDate with that selected date instead.

Step 2: Get the Millisecond Timestamp #

Once you have your full DateTime, getting the integer timestamp is straightforward—use the millisecondsSinceEpoch property:

int timestamp = combinedDateTime.millisecondsSinceEpoch;

This integer is ready to be stored directly in your database.

Pro Tip: Use UTC for Consistent Storage #

If your app will be used across time zones, it’s a good practice to store UTC timestamps to avoid confusion. To do this, convert your DateTime to UTC before grabbing the timestamp:

DateTime utcDateTime = combinedDateTime.toUtc();
int utcTimestamp = utcDateTime.millisecondsSinceEpoch;

Full Example Function #

Wrap this logic into a reusable function to keep your code clean:

int convertTimeOfDayToTimestamp(TimeOfDay time, [DateTime? customDate]) {
  // Use custom date if provided, else use current date
  DateTime date = customDate ?? DateTime.now();
  
  DateTime combinedDateTime = DateTime(
    date.year,
    date.month,
    date.day,
    time.hour,
    time.minute,
  );
  
  // Uncomment below to use UTC instead
  // return combinedDateTime.toUtc().millisecondsSinceEpoch;
  
  return combinedDateTime.millisecondsSinceEpoch;
}

Bonus: Convert Timestamp Back to TimeOfDay #

When you retrieve the timestamp from the database, you can convert it back to a TimeOfDay like this:

int storedTimestamp = 1700000000000; // From your database
DateTime retrievedDateTime = DateTime.fromMillisecondsSinceEpoch(storedTimestamp);
TimeOfDay retrievedTime = TimeOfDay.fromDateTime(retrievedDateTime);

内容的提问来源于stack exchange，提问作者Robin Sinha