FROM & TO date for BETWEEN query using DateEntry

import tkinter  as tk 
from tkcalendar import DateEntry
from datetime import date
my_w = tk.Tk()
my_w.geometry("380x220")  
sel1,sel2=tk.StringVar(),tk.StringVar()
dt2,dt2='',''
def my_upd1(*args): # triggered when value of string varaible changes
    global dt1,dt2
    if(len(sel1.get())>3):
        dt1=cal1.get_date()
        cal2.config(mindate=dt1)
        dt1 = dt1.strftime("%Y-%m-%d") # create date type
        query.set("date BETWEEN " + dt1 + " AND " + dt2)
def my_upd2(*args):
    if(len(sel2.get())>3):
        dt2=cal2.get_date()
        cal1.config(maxdate=dt2)
        dt2= dt2.strftime("%Y-%m-%d")
        query.set("date BETWEEN " + dt1 + " AND " + dt2)
def my_reset():
    dt1,dt2='',''
    dt_today=date.today().strftime('%d-%m-%Y')
    cal1.set_date(dt_today) # todays date 
    cal2.set_date(dt_today) # todays date 
    cal1.config(maxdate=None)
    cal2.config(mindate=None)    
    query.set("date BETWEEN " + dt1 + " AND " + dt2)
l_from=tk.Label(my_w,text='From',font=18)
l_from.grid(row=0,column=0)
l_to=tk.Label(my_w,text='To',font=18)
l_to.grid(row=0,column=1)
cal1=DateEntry(my_w,selectmode='day',textvariable=sel1,date_pattern='dd-MM-yyyy')
cal1.grid(row=1,column=0,padx=15)
cal2=DateEntry(my_w,selectmode='day',textvariable=sel2,date_pattern='dd-MM-yyyy')
cal2.grid(row=1,column=1,padx=15)
b1=tk.Button(my_w,text='Reset'
    ,command=lambda:my_reset())
b1.grid(row=1,column=2)
query=tk.StringVar(value='Query here')
l1=tk.Label(my_w,textvariable=query,bg='lightgreen')
l1.grid(row=2,column=0,columnspan=3,pady=10)
sel1.trace('w',my_upd1) # on change of string variable 
sel2.trace('w',my_upd2) # on change of string variable 
my_w.mainloop()