NLog.Targets.FileTarget.GetArchiveDateFormatString C# (CSharp) Method

        private string GetArchiveDateFormatString(string defaultFormat)
        {
            // If archiveDateFormat is not set in the config file, use a default 
            // date format string based on the archive period.
            string formatString = defaultFormat;
            if (string.IsNullOrEmpty(formatString))
            {
                switch (this.ArchiveEvery)
                {
                    case FileArchivePeriod.Year: formatString = "yyyy"; break;
                    case FileArchivePeriod.Month: formatString = "yyyyMM"; break;
                    default: formatString = "yyyyMMdd"; break;
                    case FileArchivePeriod.Hour: formatString = "yyyyMMddHH"; break;
                    case FileArchivePeriod.Minute: formatString = "yyyyMMddHHmm"; break;
                }
            }
            return formatString;
        }