using (var changeInfoService = new ChangeInfoService { ArticleTimeStampActive = false })
{
    part.Properties.PART_LASTCHANGE_DATE = new DateTime(1977, 4, 26);
    part.Properties.PART_LASTCHANGE_USER = "TEST_USER";
    part.Properties.ARTICLE_DESCR1 = "test_123";
}

//set properties with 'normal' timestamp settings. Will set automatically current time and user
part.Properties.PART_LASTCHANGE_DATE = new DateTime(1977, 4, 26);
part.Properties.PART_LASTCHANGE_USER = "TEST_USER";
part.Properties.ARTICLE_DESCR1 = "test_123";

//deactivate automatic change/create information update
using (var changeInfoService = new ChangeInfoService { ChangeAndCreateInfoUpdateForPage = false })
{
    //make artificial change just to check modification date and user
    var text1 = new Eplan.EplApi.DataModel.Graphics.Text();
    text1.Create(page, "", 10.0);
    text1.Remove();

    //output changes
    Console.WriteLine(page.Properties.PAGE_LASTAUTOMODIFICATIONDATE.ToString());
    Console.WriteLine(page.Properties.PAGE_LASTAUTOMODIFICATIONTIME.ToString());
    Console.WriteLine(page.Properties.PAGE_LASTMODIFICATOR.ToString());
}

var text2 = new Eplan.EplApi.DataModel.Graphics.Text();
text2.Create(page, "", 10.0);
text2.Remove();

//output changes
Console.WriteLine(page.Properties.PAGE_LASTAUTOMODIFICATIONDATE.ToString());
Console.WriteLine(page.Properties.PAGE_LASTAUTOMODIFICATIONTIME.ToString());
Console.WriteLine(page.Properties.PAGE_LASTMODIFICATOR.ToString());