直接贴代码了，你直接拷贝然后另存为html就可以用了，不多说，请看：
<!DOCTYPE html>
<html lang="en" xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta charset="utf-8" />
<title></title>
<script type="text/javascript">
function lookup() {
var d = parseFloat(document.form1.date1.value); // read date from form
var m = parseFloat(document.form1.month1.value); // read month value from form
var y = parseFloat(document.form1.year1.value); // read year from form
var a = Math.floor(y / 100);
var b = 2 - a + Math.floor(a / 4);
if (m < 3) {
var y = y - 1;
var m = m + 12;
}
jd1 = eval(Math.floor(365.25 * (y + 4716)) + Math.floor(30.6001 * (m + 1)) + d + b - 1524);
var d = parseFloat(document.form1.date2.value); // read date from form
var m = parseFloat(document.form1.month2.value); // read month value from form
var y = parseFloat(document.form1.year2.value); // read year from form
if (m < 3) {
var y = y - 1;
var m = m + 12;
}
jd2 = eval(Math.floor(365.25 * (y + 4716)) + Math.floor(30.6001 * (m + 1)) + d + b - 1524);
document.form1.answer.value = eval(Math.abs(jd1 - jd2));
}
</script>
</head>
<body>
<form name="form1">
<font color="#F9F9F9">
计算时间天数
</font>
<div align="center">
<table cellpadding="5" align="middle" border="5">
<tbody>
<tr bgcolor="#b6d4d2">
<!--ROW 1-->
<td colspan="3" bgcolor="#c3c3c3">
<center>
<font color="#FFFFFF">
<font face="Arial,Helvetica,Geneva,Swiss,SunSans-Regular">
日期
</font>天数计算器在线使用
</font>
</center>
</td>
</tr>
<!--<tr>
<td colspan="3" bgcolor="#993300">
<a title="126计算公式大全" target="_blank" href="#">
<font color="#993300">126计算公式大全</font>
</a>
</td>
</tr>-->
<tr bgcolor="#c3c3c3">
<td align="middle" colspan="3" height="33" bgcolor="#c3c3c3">
<font face="Arial,Helvetica,Geneva,Swiss,SunSans-Regular" color="#FFFFFF">
所需<a href="#" style="text-decoration: none"><font color="#FFFFFF">的数据</font></a>录入-日期相差天数
</font>
</td>
</tr>
<tr>
<td>从日期</td>
<td><select size="1" name="date1"> <option value="1" selected="" select="">1</option><option value="2">2</option><option value="3">3</option><option value="4">4</option><option value="5">5</option><option value="6">6</option><option value="7">7</option><option value="8">8</option><option value="9">9</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 size="1" name="month1"> <option value="1" selected="">一月</option><option value="2">二月</option><option value="3">三月</option><option value="4">四月</option><option value="5">五月</option><option value="6">六月</option><option value="7">七月</option><option value="8">八月</option><option value="9">九月</option><option value="10">十月</option><option value="11">十一月</option><option value="12">十二月</option></select> </td>
<td>
<select size="1" name="year1" type="text">
<option value="1970">1970</option>
<option value="1971">1971</option>
<option value="1972">1972</option>
<option value="1973">1973</option>
<option value="1974">1974</option>
<option value="1975">1975</option>
<option value="1976">1976</option>
<option value="1977">1977</option>
<option value="1978">1978</option>
<option value="1979">1979</option>
<option value="1980">1980</option>
<option value="1981">1981</option>
<option value="1982">1982</option>
<option value="1983">1983</option>
<option value="1984">1984</option>
<option value="1985">1985</option>
<option value="1986">1986</option>
<option value="1987">1987</option>
<option value="1988">1988</option>
<option value="1989">1989</option>
<option value="1990">1990</option>
<option value="1991" selected="selected">1991</option>
<option value="1992">1992</option>
<option value="1993">1993</option>
<option value="1994">1994</option>
<option value="1995">1995</option>
<option value="1996">1996</option>
<option value="1997">1997</option>
<option value="1998">1998</option>
<option value="1999">1999</option>
<option value="2000">2000</option>
<option value="2001">2001</option>
<option value="2002">2002</option>
<option value="2003">2003</option>
<option value="2004">2004</option>
<option value="2005">2005</option>
<option value="2006">2006</option>
<option value="2007">2007</option>
<option value="2008">2008</option>
<option value="2009">2009</option>
<option value="2010">2010</option>
<option value="2011">2011</option>
<option value="2012">2012</option>
<option value="2013">2013</option>
<option value="2014">2014</option>
<option value="2015">2015</option>
<option value="2016">2016</option>
<option value="2017">2017</option>
<option value="2018">2018</option>
<option value="2019">2019</option>
<option value="2020">2020</option>
<!--<option value="2021">2021</option>
<option value="2022">2022</option>
<option value="2023">2023</option>
<option value="2024">2024</option>
<option value="2025">2025</option>
<option value="2026">2026</option>
<option value="2027">2027</option>
<option value="2028">2028</option>
<option value="2029">2029</option>
<option value="2030">2030</option>
<option value="2031">2031</option>
<option value="2032">2032</option>
<option value="2033">2033</option>
<option value="2034">2034</option>
<option value="2035">2035</option>
<option value="2036">2036</option>
<option value="2037">2037</option>
<option value="2038">2038</option>
<option value="2039">2039</option>
<option value="2040">2040</option>
<option value="2041">2041</option>
<option value="2042">2042</option>
<option value="2043">2043</option>
<option value="2044">2044</option>
<option value="2045">2045</option>
<option value="2046">2046</option>
<option value="2047">2047</option>
<option value="2048">2048</option>
<option value="2049">2049</option>-->
</select>
</td>
</tr>
<tr>
<td>到<font face="Arial,Helvetica,Geneva,Swiss,SunSans-Regular">日期</font></td>
<td><select size="1" name="date2"> <option value="1" selected="" select="">1</option><option value="2">2</option><option value="3">3</option><option value="4">4</option><option value="5">5</option><option value="6">6</option><option value="7">7</option><option value="8">8</option><option value="9">9</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 size="1" name="month2"> <option value="1" selected="">一月</option><option value="2">二月</option><option value="3">三月</option><option value="4">四月</option><option value="5">五月</option><option value="6">六月</option><option value="7">七月</option><option value="8">八月</option><option value="9">九月</option><option value="10">十月</option><option value="11">十一月</option><option value="12">十二月</option></select> </td>
<td>
<select size="1" name="year2" type="text">
<option value="1970">1970</option>
<option value="1971">1971</option>
<option value="1972">1972</option>
<option value="1973">1973</option>
<option value="1974">1974</option>
<option value="1975">1975</option>
<option value="1976">1976</option>
<option value="1977">1977</option>
<option value="1978">1978</option>
<option value="1979">1979</option>
<option value="1980">1980</option>
<option value="1981">1981</option>
<option value="1982">1982</option>
<option value="1983">1983</option>
<option value="1984">1984</option>
<option value="1985">1985</option>
<option value="1986">1986</option>
<option value="1987">1987</option>
<option value="1988">1988</option>
<option value="1989">1989</option>
<option value="1990">1990</option>
<option value="1991">1991</option>
<option value="1992">1992</option>
<option value="1993">1993</option>
<option value="1994">1994</option>
<option value="1995">1995</option>
<option value="1996">1996</option>
<option value="1997">1997</option>
<option value="1998">1998</option>
<option value="1999">1999</option>
<option value="2000">2000</option>
<option value="2001">2001</option>
<option value="2002">2002</option>
<option value="2003">2003</option>
<option value="2004">2004</option>
<option value="2005">2005</option>
<option value="2006">2006</option>
<option value="2007">2007</option>
<option value="2008">2008</option>
<option value="2009">2009</option>
<option value="2010">2010</option>
<option value="2011">2011</option>
<option value="2012">2012</option>
<option value="2013">2013</option>
<option value="2014">2014</option>
<option value="2015" selected="selected">2015</option>
<option value="2016">2016</option>
<option value="2017">2017</option>
<option value="2018">2018</option>
<option value="2019">2019</option>
<option value="2020">2020</option>
<!--<option value="2021">2021</option>
<option value="2022">2022</option>
<option value="2023">2023</option>
<option value="2024">2024</option>
<option value="2025">2025</option>
<option value="2026">2026</option>
<option value="2027">2027</option>
<option value="2028">2028</option>
<option value="2029">2029</option>
<option value="2030">2030</option>
<option value="2031">2031</option>
<option value="2032">2032</option>
<option value="2033">2033</option>
<option value="2034">2034</option>
<option value="2035">2035</option>
<option value="2036">2036</option>
<option value="2037">2037</option>
<option value="2038">2038</option>
<option value="2039">2039</option>
<option value="2040">2040</option>
<option value="2041">2041</option>
<option value="2042">2042</option>
<option value="2043">2043</option>
<option value="2044">2044</option>
<option value="2045">2045</option>
<option value="2046">2046</option>
<option value="2047">2047</option>
<option value="2048">2048</option>
<option value="2049">2049</option>-->
</select>
</td>
</tr>
<tr>
<td align="middle" bgcolor="#c3c3c3" colspan="3">
<input onclick="lookup();" type="button" value="计算">
<input type="reset" value="清除">
</td>
</tr>
<tr>
<td colspan="2" bgcolor="#c3c3c3">
<p align="center">天数计算 </p>
</td>
<td>
<input size="10" name="answer">
</td>
</tr>
</tbody>
</table>
</div>
<p align="center">使用该计算器可以算出从某年某<font face="Arial,Helvetica,Geneva,Swiss,SunSans-Regular">月某日到某年某月某日的间隔天数差</font></p>
</form>
</body>
</html>