import datetime
from tkinter import *
from time import *

def show_time():
    buff.set(strftime('%H:%M:%S (%a %d %b %Y)'))
    root.after(1000, show_time)

def WHATDAY(yy,mm,dd):
    #***********************************
    # Zeller's congruence
    #***********************************
    # int_day=1 to 7 => Mon to Sun
    cc=int(yy/100)
    pp=dd+int(26*(mm+1)/10)+int(yy%100)+int((yy%100)/4)+(5*cc+int(cc/4))+5
    int_day=int(pp%7)+1
    return int_day

def LEAP_YEAR(yy):
    LEAP_YEAR=0
    if yy%400==0 or (yy%4==0 and yy%100!=0): LEAP_YEAR=1
    return LEAP_YEAR

def CALC(yy,mm,dd,ddate):
    m_days=[31,28,31,30,31,30,31,31,30,31,30,31]
    cal=[[0]*7 for i in range(0,6)]
    yc=yy
    mc=mm
    if mm==1: yc=yy-1; mc=13
    if mm==2: yc=yy-1; mc=14
    int_day=WHATDAY(yc,mc,dd)
    ly=LEAP_YEAR(yy)
    if ly==1 and mm==2: m_days[1]=29
    if ly==0 and (mc==14 and dd==29):
        print('Date inputted is invalid!')
    ir=-1
    ic=-1
    k=0
    for i in range(1,m_days[mm-1]+1):
        int_day=WHATDAY(yc,mc,i)
        cal[k][int(int_day)-1]=i
        if ddate.year==yy and ddate.month==mm and ddate.day==i: ir=k; ic=int(int_day)-1
        if int_day==7: k=k+1
    nw=5
    if cal[5][0]!=0: nw=6
    return nw,cal,ir,ic

def CH_L():
    global yi,yd,dy,t2
    dy=dy-1
    yd=yi+dy
    t2.destroy()
    DRAWCAL()

def CH_R():
    global yi,yd,dy,t2
    dy=dy+1
    yd=yi+dy
    t2.destroy()
    DRAWCAL()

def CH_C():
    global yi,yd,dy,t2
    dy=0
    yd=yi
    t2.destroy()
    DRAWCAL()

def DRAWCAL():
    global yd,t2
    ddate=datetime.datetime.today()
    t2=Frame(root,bg='#ffffff')
    t2.pack(side=TOP,fill=BOTH)
    hh=yd-2000+12
    col1='#ffffdd'
    col2='#000088'
    str1=str(yd)+' (H'+str(hh)+')'
    Label(t2,text=str1,bg=col1,fg=col2,font='consolas 11 bold',relief=FLAT).grid(row=0,column=0,columnspan=3,sticky=W+E)
    m_list=['Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec']
    w_list=['M','T','W','T','F','S','S']
    col1='#ffffff'
    col2='#000000'
    colbg1=['#ffffff','#ffffff','#ffffff','#ffffff','#ffffff','#0000ff','#ff0000']
    colfg1=['#000000','#000000','#000000','#000000','#000000','#ffffff','#ffffff']
    colbg2=['#ffffff','#ffffff','#ffffff','#ffffff','#ffffff','#ffffff','#ffffff']
    colfg2=['#000000','#000000','#000000','#000000','#000000','#0000ff','#ff0000']
    nw=6
    k=0
    for i in range(0,4):
        for j in range(0,3):
            k=k+1
            col1='#ffffff'
            col2='#000000'
            _mm=Frame(t2,bg=col1,relief=RAISED)
            str2=m_list[k-1]
            Label(_mm,text=str2,bg=col1,fg=col2,font='consolas 11 bold',relief=FLAT,bd=0).grid(row=0,column=0,columnspan=7)
            for c,wd in enumerate(w_list):
                col1=colbg1[c]
                col2=colfg1[c]
                str3=wd
                Label(_mm, text=str3, bg=col1, fg=col2,font='consolas 10 bold',relief=FLAT,bd=0).grid(row=1,column=c,padx=0,pady=0)
            dum,cal,ir,ic=CALC(yd,k,1,ddate)
            for r in range(nw):
                for c in range(7):
                    col1=colbg2[c]
                    col2=colfg2[c]
                    if cal[r][c]==0: str4='  '
                    else: str4='{0:2d}'.format(cal[r][c])
                    if 0<=ir and 0<=ic:
                        if r==ir and c==ic: col1='#808000'; col2='#ffffff'
                    Label(_mm, text=str4, bg=col1, fg=col2,font='consolas 10 bold',relief=FLAT,bd=0).grid(row=r+2,column=c,padx=0,pady=0)
            _mm.grid(row=i+1,column=j,padx=3,pady=0)
    del m_list,w_list,colbg1,colbg2,colfg1,colfg2,cal

#Main routine
d=datetime.datetime.today()
yi=d.year
dy=0
yd=yi

root=Tk()
t1=Frame(root)
t1.pack(side=TOP,fill=BOTH)
buff = StringVar()
buff.set('')
Button(t1,text='<',font='consolas 14 bold',command=CH_L).pack(side=LEFT)
Button(t1,textvariable=buff,font='consolas 14 bold',width=30,command=CH_C).pack(side=LEFT,fill=X)
Button(t1,text='>',font='consolas 14 bold',command=CH_R).pack(side=RIGHT)
show_time()
DRAWCAL()
root.mainloop( )