html code:
<html>
    <head>
        <link rel="stylesheet" href="tabulas.css">
    </head>
    <body>
        <table>
            <caption>Šis ir tabulas virsraksts, kas aizņem tabulas platumu un centrējas</caption>
            <colgroup>
                <col span="2">
            </colgroup>
            <tbody>
            <tr>
                <td>18</td>
                <td></td>
                <td></td>
                <td></td>
                <td>1</td>
                <td>2</td>
                <td>3</td>
                <td>4</td>
            </tr>
            <tr>
                <td>19</td>
                <td>5</td>
                <td>6</td>
                <td>7</td>
                <td>8</td>
                <td>9</td>
                <td>10</td>
                <td>11</td>
            </tr>
            <tr>
                <td>20</td>
                <td>12</td>
                <td>13</td>
                <td>14</td>
                <td>15</td>
                <td>16</td>
                <td>17</td>
                <td>18</td>
            </tr>
            <tr>
                <td>21</td>
                <td>19</td>
                <td>20</td>
                <td>21</td>
                <td>22</td>
                <td>23</td>
                <td>24</td>
                <td>25</td>
            </tr>
            <tr>
                <td>22</td>
                <td>26</td>
                <td>27</td>
                <td>28</td>
                <td>29</td>
                <td>30</td>
                <td>31</td>
                <td></td>
            </tr>
            </tbody>
            <thead>
                <tr>
                    <th rowspan="2">Nedeļa</th>
                    <th colspan="7">2025. gada maijs</th>
                </tr>
                <tr>
                    <th>Pirmdiena</th>
                    <th>Otradiena</th>
                    <th>Trešdiena</th>
                    <th>Ceturtdiena</th>
                    <th>Piektdiena</th>
                    <th>Sestdiena</th>
                    <th>Svētdiena</th>
                </tr>
            </thead>
        </table>
    </body>
</html>

css code:
table {
    width: 1000px;
    border: 3px dotted blue;
    padding:5px;
    border-spacing: 5px;
}
th,td {
    border: 1px solid black;
}
td:nth-child(1) {
    background-color: lime;
    text-align: center;
    color: pink;
    height: 10px;
}
tr:nth-child(2) th:nth-child(even) {
    background-color: green;
    color: white;
}
tr:nth-child(1) th:nth-child(2) {
    background-color: green;
    color: white;
    height: 75px;
    font-size: 30px;
}
tr:nth-child(2) th:nth-child(odd) {
    background-color: blue;
    color: pink;
}
tr:nth-child(1) th:nth-child(1) {
    background-color: rgb(0, 140, 255);
    color: pink;
}
td:nth-child(7), td:nth-child(8) {
    background-color: yellow;
}