Comandos referente a datas no C#

Trocar barras de uma data que esta numa string por traço:

string sVariavelNova = DateTime.Now.ToString("yyyy/MM/dd").Replace("/", "-");

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Capturar data do sistema com o formato ano/mês/dia no C#:

DateTime.Now.ToString("yyyy/MM/dd");

DateTime.Now.ToString("HH:mm:ss");

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Outra maneira de manipular datas:

string dia = DateTime.Now.Day.ToString();

string mes = DateTime.Now.Month.ToString();

string ano = DateTime.Now.Year.ToString();

string VDataDoSistema = dia+mes+ano;

string VHoraSistema = DateTime.Now.ToShortTimeString();

string VDataDoSistema = DateTime.Now.ToString("yyyy/MM/dd");

string VHoraSiistema = DateTime.Now.ToString("HH:mm:ss");

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if(DateTime.Today.Month > datePicker.Value.Month && DateTime.Today.Day > datePicker.Value.Day)

anos = DateTime.Today.Year - datePicker.Value.Year;

else

anos = DateTime.Today.Year - datePicker.Value.Year - 1;