Leen's name day is celebrated on July 22nd in Estonia.
Leen is a relatively uncommon given name in the United States, often perceived as having a soft and perhaps slightly international feel. Its origins are varied, sometimes appearing as a short form or variant of names like Eileen or Helena, with potential connections to Irish or Greek roots meaning "light" or "shining one." In terms of tone, Leen tends to evoke a sense of gentle elegance rather than strength or playfulness. While it can be used for any gender, it is more frequently encountered as a feminine name in American contexts. Due to its rarity, the name often carries a unique and somewhat melodic quality.
| Country | Day | Month | Names |
 USA | 1 | January | Arleen, Arlen, Arlene, Arlette, Pablo, Paul, Saul |
| USA | 28 | January | Carlotta, Charleen, Charlene, Charlotta, Charlotte, Charmaine, Manfred |
| USA | 23 | April | Brayan, Breana, Breanna, Breanne, Brian, Briana, Brianna, Brianne, Brielle, Brien, Briona, Bryan, Bryana, Bryanna, Bryant, Brynn, Bryon, Shirlee, Shirleen, Shirley |
| USA | 22 | May | Jolee, Joleen, Jolene, Jolie, Marshall |
| USA | 25 | May | Madalyn, Madeleine, Madeline, Madelyn, Madilyn, Marlee, Marleen, Marlena, Marlene, Marley |
| USA | 28 | June | Dara, Darla, Darleen, Darlene, Darrell, Darren, Darrin, Darryl, Daryl, Jarell, Jerrell |
 Finland | 22 | July | Leena, Leeni, Lenita, Matleena |
 Estonia | 18 | August | Heleene, Helene, Helena, Elina, Ilona, Helen, Hell, Hella, Helle, Hellen, Helli |
| USA | 18 | August | Aileen, Eileen, Elaina, Elaine, Eleanor, Elena, Eliana, Ella, Elle, Ellen, Ellie, Helen, Helena, Iliana, Lena, Leonora, Nell, Nellie, Nelly |
| USA | 12 | November | Colan, Colin, Colleen, Collin, Cullan, Cullen, Culver, Kiley, Kyla, Kyle, Kylee, Kyleigh, Kyler, Kylier |
| USA | 25 | November | Caitlin, Caitlyn, Carina, Caryn, Catherine, Cathleen, Cathy, Kaitlin, Kaitlynn, Kara, Karen, Kari, Karina, Kate, Katelyn, Katelynn, Katharine, Katherine, Kathleen, Kathryn, Kathy, Katie, Katrina, Treena, Trina, Trinity |