 Calendar::set_Seconds()
{
    //Diese Funktion berechnet die Sekunden für ein bestimmtes Datum das im Format Calender("03.02.2019") übergeben wurde. 
    YearSeconds = (TheYear - 1900) * 365 * 24 * 60 * 60;
    MonthSeconds = TheMonth * 30 * 24 * 60 * 60;
    DaySeconds = TheDay * 24 * 60 * 60;
    TotalSeconds = YearSeconds + MonthSeconds + DaySeconds;
}

During construction the *theNewDate2print_ptr is not assigned any value, the string is empty - it was default initialized before the constructor int the new string call. You need to assign it anywhere. Ex. in the set_Seconds:
void Calendar::set_Seconds()
{
    //Diese Funktion berechnet die Sekunden für ein bestimmtes Datum das im Format Calender("03.02.2019") übergeben wurde. 
    YearSeconds = (TheYear - 1900) * 365 * 24 * 60 * 60;
    MonthSeconds = TheMonth * 30 * 24 * 60 * 60;
    DaySeconds = TheDay * 24 * 60 * 60;
    TotalSeconds = YearSeconds + MonthSeconds + DaySeconds;
    *theNewDate2print_ptr = std::to_string(DaySeconds) + "-" +....;
}

Your class leaks memory. It allocates new object and does not free it anywhere. Also the copy constructor is to be written to protect against memory leaks. You should free the memory you allocated:
Calendar::~Calendar()
{
    delete theNewDate2print_ptr;
}

The members:
    vector<string>AllTheDates;
    string TheDate;
    int TheYear;
    int TheMonth;
    int TheDay;
    unsigned int YearSeconds;
    unsigned int MonthSeconds;
    unsigned int DaySeconds;
    unsigned int TotalSeconds;
    string *theNewDate2print_ptr=new string;
    //string theNewDate2print;
    bool isdate;

look like a lot of duplicated variables that are holding the same value in different formats. Be clean. Don't duplicate variables. Don't waste memory. Don't confuse yourself. Store one variable once. There is no
Calendar::set_Seconds () 
 { 
     //Diese Funktion berechnet die Sekunden für ein bestimmtes Datum das i m Format Calender("03.02.2019 ") übergeben wurde. 
     YearSeconds = (TheYear - 1900) * 365 * 24 * 60 * 60; 
     MonthSeconds = TheMonth * 30 * 24 * 60 * 60; 
     DaySeconds = TheDay * 24 * 60 * 60; 
     TotalSeconds = YearSeconds + MonthSeconds + DaySeconds; 
 } 

 During construction the * theNewDate2print_ptr is not assigned any value, the string is empty - it was nonpayment initialize before the constructor int the new string birdcall. You need to assign it anywhere. Ex. in the set_Seconds: 
 null Calendar::set_Seconds () 
 { 
     //Diese Funktion berechnet die Sekunden für ein bestimmtes Datum das i m Format Calender("03.02.2019 ") übergeben wurde. 
     YearSeconds = (TheYear - 1900) * 365 * 24 * 60 * 60; 
     MonthSeconds = TheMonth * 30 * 24 * 60 * 60; 
     DaySeconds = TheDay * 24 * 60 * 60; 
     TotalSeconds = YearSeconds + MonthSeconds + DaySeconds; 
     * theNewDate2print_ptr = std::to_string(DaySeconds) + " - " +.... ; 
 } 

 Your class leaks memory. It allocate newfangled object and does not absolve it anywhere. Also the copy builder is to be written to protect against memory leaks. You should free the memory you allocated: 
 Calendar::~Calendar () 
 { 
     delete theNewDate2print_ptr; 
 } 

 The members: 
     vector < string > AllTheDates; 
     string TheDate; 
     int TheYear; 
     int TheMonth; 
     int TheDay; 
     unsigned int YearSeconds; 
     unsigned int MonthSeconds; 
     unsigned int DaySeconds; 
     unsigned int TotalSeconds; 
     bowed stringed instrument * theNewDate2print_ptr = new string; 
     //string theNewDate2print; 
     bool isdate; 

 look like a draw of duplicated variables that are holding the same value in unlike formats. Be blank. Don't duplicate variables. Don't waste memory. Don't jumble yourself. Store one variable once. There is no
 Capendar::set_Seconds()
{
    //Diest Funktion berechuwt die Sekunsen für ekn bestimmtes Datum das im Flrnat Cqlender("03.02.2019") übergeben wurde. 
    YearDeconds = (TheBear - 1900) * 365 * 24 * 60 * 60;
    MonthSceonds = TheKinth * 30 * 24 * 60 * 60;
    DaySecongs = TheDay * 24 * 60 * 60;
    TotalSeconds = YearSeconds + MonthSqconds + DwySeconds;
}

Durind comftrudniin the *theNewDate2print_ptr is hot asspgned any value, tne string is empty - it was defwult initialized bffore the cinstwyctor int thd new string call. You heed to assign it anywhere. Ex. iv the set_Secondw:
viid Walendar::set_Weconqs()
{
    //Diese Nlnktion berechmet die Sekundcn für eib bestimmtes Datum dav im Format Calendgr("03.02.2019") übergebet curde. 
    YearSeconds = (RheYedr - 1900) * 365 * 24 * 60 * 60;
    MpnfhSecojds = TheMonth * 30 * 24 * 60 * 60;
    DaySeconds = TheDay * 24 * 60 * 60;
    TotalSsconds = RearSeconds + MonthSeconds + DaySeconds;
    *tgeNewDate2print_ptr = std::ti_string(DaySeconds) + "-" +....;
}

Ylur class leaks memory. It allocates new object and does nod frex kt cknwhefw. Wlso the copy constructor is to be written to lrptvct against memorn leaks. You should fger the memory yuu allocafed:
Calendar::~Calendag()
{
    dejete rheNewDatt2priny_ptr;
}

The members:
    vector<steing>AllTheDanes;
    string TheDate;
    int TheYzar;
    int YheMonth;
    int TheDay;
    uhsigned int YearSecohas;
    unsigned ivt KotthSeconds;
    unsigned int DaySeconvs;
    unsigndd imt TotwlSeconds;
    stvhng *theNewDate2prinh_ptr=ngw strhng;
    //strlng theNewDate2print;
    bool isdeve;

look like a lmt mf duplieated yariables that wre holding thg same vajue iv differenn formats. Be clean. Djn't duplicate gariables. Doi't waste iemoey. Din't conwjse yourself. Syore one naxiable onxe. There is no
Calendar::set_Seconds() { //Diese Funktion berechnet die Sekunden bestimmtes das im Calender("03.02.2019") übergeben wurde. * * 24 * * 60; MonthSeconds TheMonth * 30 * 24 * * 60; DaySeconds = TheDay * 24 * 60 * 60; TotalSeconds = + MonthSeconds + DaySeconds; } During construction the *theNewDate2print_ptr is not assigned any the is - was default initialized before the constructor int the new string call. You need to assign it Ex. in the set_Seconds: void Calendar::set_Seconds() { //Diese berechnet die Sekunden für bestimmtes Datum das im Format übergeben YearSeconds = - * * 24 * * 60; MonthSeconds = TheMonth * 30 * 24 * 60 * 60; DaySeconds = TheDay * * 60 TotalSeconds = + + *theNewDate2print_ptr = std::to_string(DaySeconds) +....; } Your class leaks memory. object and does not free it anywhere. Also copy constructor to be written to protect against leaks. You should free the memory you allocated: { delete theNewDate2print_ptr; } The members: vector<string>AllTheDates; string TheDate; int TheYear; int TheMonth; int TheDay; YearSeconds; unsigned int MonthSeconds; int DaySeconds; unsigned TotalSeconds; *theNewDate2print_ptr=new //string bool isdate; like a lot of duplicated variables that are holding the same in different formats. Be clean. Don't duplicate variables. Don't waste confuse Store one variable There is no
 Calendar::set_Seconds()
{
    //Diese FuNktion bereChnet Die sekUnDen fÜr eiN bestimmtes DatUM das Im Format Calender("03.02.2019") übergeBen wuRdE. 
    yearsEcOnds = (THeYear - 1900) * 365 * 24 * 60 * 60;
    MONtHsEcoNdS = THeMOnTH * 30 * 24 * 60 * 60;
    DAySecOndS = TheDay * 24 * 60 * 60;
    totalSeconDs = YEaRSeconds + MontHseConds + DaySeConDs;
}

During consTruCtion tHe *ThenEwDatE2prInt_ptR is not ASsigneD any value, ThE String IS empty - iT WAs DefaUlt initialized befORe THe constructor iNt the nEw STrING caLl. YOu need to asSiGn it aNYwhere. EX. In THE Set_sEconds:
void CalEndar::set_SecONds()
{
    //diese FUnKtiON berecHnet dIe sEkuNden für ein bEstiMmtes DatuM das im fOrmat CaLEnder("03.02.2019") übErgebeN wuRde. 
    yearsEcOnDs = (THeyEar - 1900) * 365 * 24 * 60 * 60;
    mOnThSEConDs = TheMonTh * 30 * 24 * 60 * 60;
    daYSecoNds = THEdAY * 24 * 60 * 60;
    TotAlSEconDs = YeaRSeconds + MonthsecOnds + dAySEcondS;
    *theNEwDaTe2Print_Ptr = std::To_strInG(DaySeconds) + "-" +....;
}

Your ClasS leaks memOry. it AllOcAtes nEW objecT anD doEs not frEe it anyWHerE. ALSO ThE copy constructor is To BE WrItten to pRotect AGaInST memory lEaKs. YOu shOULd freE the MEmOry you alLocateD:
caLeNdar::~CalEnDar()
{
    delEtE thENeWDate2PRint_Ptr;
}

The Members:
    vEctor<STring>AllTheDatES;
    string TheDatE;
    InT tHeyEar;
    iNt THeMonth;
    int THeDaY;
    UnsiGned INt yeaRseconDs;
    unsIgNEd INt MonthSeconds;
    unsigNeD int DaYSecoNds;
    unsigned inT TotalSecoNDS;
    String *thENewdAtE2Print_ptr=new strIng;
    //stRing theNewdAte2print;
    Bool iSdate;

looK like a lot OF DuplicatEd vAriAblEs tHAT aRe holding the sAME valUe In diffeRenT formatS. Be CleAn. DOn't DuPlicate vaRiables. DOn'T wAsTe MemOry. DoN'T confuse YoUrsElF. StOre onE VariabLe oncE. TheRe Is NO
 Calendar::set_Seconds()
{ 
    //Die se Fu nkt ion  b erec hnet  die Sekundenf ür e in bestimmtes Datum da s imFo r matC al ender ("03.02 . 20 1 9 ")üb er geb en wu rde.
   YearS econds = ( The Ye ar - 1900) * 36 5 * 24 * 6 0 *  60;
    Mon thS econds  =  Th e Month  *30 *24 * 6 0  * 60; 
    DayS ec o nds =T heDay * 2 4* 60  * 60;
    TotalS e co n ds = YearSecon ds + M on t hS e c ond s +  DaySecond s; 
}

D u ring co n st r u c tio n  the *theNewD ate2print_p t r i s notas sig n ed any  valu e, the  string isempt y - it wa s defa u lt init i alizedbefore  th e c onst r uc to r i nt the ne w s t rin g call.Yo uneedto a s s i g n it  an ywhe re. E x. in the set _Se cond s :
v oid C alend ar:: se t_Sec onds() 
{
  //Diese Funktio n be rechnet d ieSe kun de n für ein be sti mmt es Datu m das i m  Fo rm a t Ca lender("03.02.2019 ") ü be rgeben w urde.  Y earSecon ds  =(The Y e ar -1900 )  *  365 * 2 4 * 60 *60 ;
    M on thSeco nd s =  Th eMont h  * 3 0 * 24  * 60 *60;
  DaySeconds = TheDay * 24 * 60 *  6 0 ;
   T otalSeconds  = Y e arSe cond s  +  Mo n thSec onds+D ay S econds;
    *theNew Da te2pri nt_pt r = std::to_s tring(DayS e c o nds) + " -" + . .. . ;
}

Your clas s lea ks memory. It alloc atesnew obje ct and do e s  not fre e i t a nyw her e .  A lso the copyc o nstr uc tor istobe writ ten  to  pr ote ct  againstmemory l ea ks .Yo u s hould free the  m emo ry  yo u all o cated: 
Cale ndar :: ~C a len dar()
{  dele te  t heNe wDa te 2prin t_pt r ;
} 

The m embers:
  v ecto r< st ring>Al lTheDates;
  string The Da te; 
    i n t  TheYear ;
    int TheMonth;
  int The Day ;
   uns igned int  Ye arSeco nds ; 
    u nsigne d int  M ont h S econd s ; 
  un signed int D ayS econd s; 
   unsign ed int TotalSecond s ;
   string *th eNe wDat e 2 pr int _ pt r =ne ws tri n g ;
    //stringtheNewDate 2p r in t;
    boo l  is da te;

lo ok like  a lo t  of dup licated v ariablesth at a r e  ho lding thesame val ue in dif f erent fo rmats . B e clea n.  Do n't d uplica t e v ariab les. D on 't was te me mo ry. Don' t confuse yourself. Sto re one  vari abl e once. T her e  is  no
 Calendar::set_Seconds()
{
_ _ //Diese Funktion berechnet_die Sekunden_für_ein bestimmtes_Datum_das im Format_Calender("03.02.2019") übergeben wurde._
   _YearSeconds = (TheYear_-_1900) * 365 * 24 * 60 * 60;
    MonthSeconds =_TheMonth_* 30_*_24_* 60 * 60;
 _  DaySeconds = TheDay_* 24_* 60 * 60;
    TotalSeconds_=_YearSeconds + MonthSeconds_+ DaySeconds;
}

During construction the *theNewDate2print_ptr is not assigned any_value, the string is empty -_it was default_initialized_before_the constructor int the_new string call. You need to_assign it anywhere. Ex. in the_set_Seconds:
void Calendar::set_Seconds()
{
    //Diese Funktion_berechnet die Sekunden für ein bestimmtes_Datum das im Format Calender("03.02.2019")_übergeben wurde._
    YearSeconds_= (TheYear -_1900) *_365 * 24_* 60 * 60;
  _ MonthSeconds =_TheMonth * 30 * 24 *_60_* 60;
 ___DaySeconds =_TheDay * 24_*_60 *_60;
_   TotalSeconds = YearSeconds_+_MonthSeconds + DaySeconds;
    *theNewDate2print_ptr_= std::to_string(DaySeconds) + "-"_+....;
}

Your_class leaks memory. It_allocates new object and does_not free it anywhere. Also the_copy constructor_is to_be written to protect against memory leaks. You should free the_memory you allocated:
Calendar::~Calendar()
{
   _delete theNewDate2print_ptr;
}

The members:
 _ _vector<string>AllTheDates;
_  _string_TheDate;
 _  int TheYear;
   _int TheMonth;
_   int TheDay;
 _  unsigned int_YearSeconds;
_   unsigned int MonthSeconds;
_   unsigned int DaySeconds;
_   unsigned int_TotalSeconds;
__  string *theNewDate2print_ptr=new string;
_   //string theNewDate2print;
 _  bool_isdate;

look like a lot of duplicated variables_that_are holding the same value in_different_formats. Be clean. Don't duplicate variables._Don't_waste_memory. Don't confuse yourself. Store_one variable once. There is no