C # Date Time formatting

Format pattern (set date 2016-10-19 15:53:29)
D	One day of the month. One-digit date has no leading zeros.
Dd	One day of the month. A one-digit date has a leading zero.
Ddd	Abbreviated name of the day of the week, defined in Abbreviateddaynames. (Wednesday)
dddd	The full name of the day of the week, as defined in DayNames. (Wednesday)
M	Month number. One-digit month has no leading zeros.
Mm	Month number. One-digit month has a leading zero.
MMM	Abbreviated name of the month, defined in AbbreviatedMonthNames. (October)
MMMM	The full name of the month, as defined in MonthNames. (October)
Y	The year that does not contain eras. If the year that does not contain an era is less than 10, the year is displayed without leading zeros.
Yy	The year that does not contain eras. If the year that does not contain an era is less than 10, the year with leading zeros is displayed.
Y	The year that includes the four-digit era.
Gg	Period or epoch. If the date to be formatted does not have an associated period or era string, the pattern is ignored.
H	12-hour hour. One-digit hours do not have leading zeros.
hh	12-hour hour. One-digit hours have leading zeros.
H	24-hour hour. One-digit hours do not have leading zeros.
HH	24-hour hour. One-digit hours have leading zeros.
M	Minutes. A single-digit number of minutes does not have a leading zero.
Mm	Minutes. A single-digit number of minutes has a leading zero.
S	Seconds. The number of seconds in a single digit does not have a leading zero.
Ss	Seconds. The number of seconds of one digit has a leading zero.
F	The fractional precision of the second is one bit. The remaining digits are truncated.
Ff	The fractional seconds precision is two bits. The remaining digits are truncated.
Fff	The fractional seconds precision is three bits. The remaining digits are truncated.
Ffff	The fractional seconds precision is four bits. The remaining digits are truncated.
Fffff	The fractional seconds precision is five bits. The remaining digits are truncated.
Ffffff	The fractional seconds precision is six bits. The remaining digits are truncated.
Fffffff	The fractional seconds precision is seven bits. The remaining digits are truncated.
T	The am/pm defined in AMDesignator or PMDesignator indicates the first character of the item, if one exists.
T T	The am/pm that is defined in AMDesignator or pmdesignator, if present.
Z	The time zone offset ("+" or "-" followed by hours only). One-digit hours do not have leading zeros. For example, Pacific Standard Time is "-8".
Zz	The time zone offset ("+" or "-" followed by hours only). One-digit hours have leading zeros. For example, Pacific Standard Time is "-08".
zzz	The full time zone offset ("+" or "-" followed by hours and minutes). The number of hours and minutes of a single digit has a leading zero. For example, Pacific Standard Time is " -08:00".
:	The default time delimiter that is defined in TimeSeparator.
/	The default date delimiter that is defined in DateSeparator.

% c where C is the format pattern (if used alone). You can omit the "%" character if the format pattern is merged with literal characters or other format patterns.
c where c is any character. Displays the characters as they are originally defined. To display a backslash character, use "\".

1. Convert 20161012 to date time

DateTime dt = Convert.todatetime (DateTime.ParseExact (STRRQ, "YYYYMMDDHHMM", null). ToString ("Yyyy-mm-dd hh:mm"));

DateTime dt = Convert.todatetime (DateTime.ParseExact (STRRQ, "YYYYMMDD", null). ToString ("Yyyy-mm-dd"));

C # Date Time formatting