Time Keeping

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Built-in Time Service

You can simply get the current time using DateTime.Now. The system starts counting at a fixed time on every power up, meaning the time ticks every second correctly but the time will be off. If the correct time is needed, the time needs to be set to the current true time (and date). This is accomplished using GHIElectronics.TinyCLR.Native.SystemTime.SetTime(DateTime utcTime)

using System;
using System.Diagnostics;
using System.Threading;

class Program {
    static void Main() {
        Debug.WriteLine("Time at power up: " + DateTime.Now);
        // January 1st 2019 at 11:11:11
        DateTime MyTime = new DateTime(2019, 1, 1, 11, 11, 11);
        GHIElectronics.TinyCLR.Native.SystemTime.SetTime(MyTime);
        while (true) {
            Debug.WriteLine("Current Time: " + DateTime.Now);
            Thread.Sleep(1000);
        }
    }
}

The output looks like

Time at power up: 01/01/2017 00:00:01
Current Time: 01/01/2019 11:11:11
Current Time: 01/01/2019 11:11:12
Current Time: 01/01/2019 11:11:13
Current Time: 01/01/2019 11:11:14
...

Real Time Clock

The Real Time Clock (RTC) is a circuit that runs off a small battery or a super capacitor. It has its own crystal and keeps runnning even when the system is powered off. Not every hardware has a built in RTC, so check your hardware's manual for more details.

In the even the RTC battery was drained or the RTC was never initialized, the RTC will not have a correct value. Use the rtc.IsValid to dermine of time is was set correctly.

using GHIElectronics.TinyCLR.Devices.Rtc;
using GHIElectronics.TinyCLR.Native;
using System;
using System.Diagnostics;
using System.Threading;

class Program {
    static void Main() {
        var rtc = RtcController.GetDefault();
        if (rtc.IsValid) {
            Debug.WriteLine("RTC is Valid");
            // RTC is good so let's use it
            SystemTime.SetTime(rtc.Now);
        }
        else {
            Debug.WriteLine("RTC is Invalid");
            // RTC is not valid. Get user input to set it
            // This example will simply set it to January 1st 2019 at 11:11:11
            var MyTime = new DateTime(2019, 1, 1, 11, 11, 11);
            rtc.Now = MyTime;
            SystemTime.SetTime(MyTime);
        }

        while (true) {
            Debug.WriteLine("Current Time    : " + DateTime.Now);
            Debug.WriteLine("Current RTC Time: " + rtc.Now);
            Thread.Sleep(1000);
        }
    }
}

The output will show both times and they should match. The first time maybe invalid and the time is set but the second power up will show the correct time.

RTC is Valid
Current Time    : 01/01/2019 11:15:35
Current RTC Time: 01/01/2019 11:15:35
Current Time    : 01/01/2019 11:15:36
Current RTC Time: 01/01/2019 11:15:36