Filling out form in Mechanical Soup with 3 values for 1 name attribute

Question

I'm trying to fill out a form using Mechanical Soup, I've been able to fill out all the other parts except for the Date of Birth because it has no name attribute for each value. This is form summary for the Date of Birth field.

I have tried to input all 3 values with the same name attribute but it doesn't seem to work either. browser.['User.Birthdate'] = '7', '10', '2000' "User.Birthdate" seems to be the name attribute but it the form doesn't get filled.

<input aria-hidden="true" data-id="hiddenDate" data-val="true" data-val-date="The field Date of Birth must be a date." data-val-daterange="Date of Birth is invalid" data-val-required="Date of Birth is required" id="User_Birthdate" name="User.Birthdate" style="display:none;" type="text" value=""/>
<select aria-labelledby="user-birthdate-label" class="select-date-month" id="PL_User_Birthdate_month"><option value="0">Month</option><option value="1">January</option><option value="2">February</option><option value="3">March</option><option value="4">April</option><option value="5">May</option><option value="6">June</option><option value="7">July</option><option value="8">August</option><option value="9">September</option><option value="10">October</option><option value="11">November</option><option value="12">December</option></select>
<select aria-labelledby="user-birthdate-label" class="select-date-day" id="PL_User_Birthdate_day"><option value="0">Day</option><option value="1">01</option><option value="2">02</option><option value="3">03</option><option value="4">04</option><option value="5">05</option><option value="6">06</option><option value="7">07</option><option value="8">08</option><option value="9">09</option><option value="10">10</option><option value="11">11</option><option value="12">12</option><option value="13">13</option><option value="14">14</option><option value="15">15</option><option value="16">16</option><option value="17">17</option><option value="18">18</option><option value="19">19</option><option value="20">20</option><option value="21">21</option><option value="22">22</option><option value="23">23</option><option value="24">24</option><option value="25">25</option><option value="26">26</option><option value="27">27</option><option value="28">28</option><option value="29">29</option><option value="30">30</option><option value="31">31</option></select>
<select aria-labelledby="user-birthdate-label" class="select-date-year" id="PL_User_Birthdate_year"><option value="0">Year</option><option value="2002">2002</option><option value="2001">2001</option><option value="2000">2000</option><option value="1999">1999</option><option value="1998">1998</option><option value="1997">1997</option><option value="1996">1996</option><option value="1995">1995</option><option value="1994">1994</option><option value="1993">1993</option><option value="1992">1992</option><option value="1991">1991</option><option value="1990">1990</option><option value="1989">1989</option><option value="1988">1988</option><option value="1987">1987</option><option value="1986">1986</option><option value="1985">1985</option><option value="1984">1984</option><option value="1983">1983</option><option value="1982">1982</option><option value="1981">1981</option><option value="1980">1980</option><option value="1979">1979</option><option value="1978">1978</option><option value="1977">1977</option><option value="1976">1976</option><option value="1975">1975</option><option value="1974">1974</option><option value="1973">1973</option><option value="1972">1972</option><option value="1971">1971</option><option value="1970">1970</option><option value="1969">1969</option><option value="1968">1968</option><option value="1967">1967</option><option value="1966">1966</option><option value="1965">1965</option><option value="1964">1964</option><option value="1963">1963</option><option value="1962">1962</option><option value="1961">1961</option><option value="1960">1960</option><option value="1959">1959</option><option value="1958">1958</option><option value="1957">1957</option><option value="1956">1956</option><option value="1955">1955</option><option value="1954">1954</option><option value="1953">1953</option><option value="1952">1952</option><option value="1951">1951</option><option value="1950">1950</option><option value="1949">1949</option><option value="1948">1948</option><option value="1947">1947</option><option value="1946">1946</option><option value="1945">1945</option><option value="1944">1944</option><option value="1943">1943</option><option value="1942">1942</option><option value="1941">1941</option><option value="1940">1940</option><option value="1939">1939</option><option value="1938">1938</option><option value="1937">1937</option><option value="1936">1936</option><option value="1935">1935</option><option value="1934">1934</option><option value="1933">1933</option><option value="1932">1932</option><option value="1931">1931</option><option value="1930">1930</option><option value="1929">1929</option><option value="1928">1928</option><option value="1927">1927</option><option value="1926">1926</option><option value="1925">1925</option><option value="1924">1924</option><option value="1923">1923</option><option value="1922">1922</option><option value="1921">1921</option><option value="1920">1920</option><option value="1919">1919</option><option value="1918">1918</option><option value="1917">1917</option><option value="1916">1916</option><option value="1915">1915</option><option value="1914">1914</option><option value="1913">1913</option><option value="1912">1912</option><option value="1911">1911</option><option value="1910">1910</option><option value="1909">1909</option><option value="1908">1908</option><option value="1907">1907</option><option value="1906">1906</option><option value="1905">1905</option><option value="1904">1904</option><option value="1903">1903</option><option value="1902">1902</option><option value="1901">1901</option><option value="1900">1900</option><option value="1899">1899</option></select>