The electric quadrupole moment for the 4dD5/22 state of Sr+88; one of the most important candidates for an optical clock, has been calculated using the relativistic coupled-cluster theory. This is the first application of this theory to determine atomic electric quadrupole moments. The result of the calculation is presented and the important many-body contributions are highlighted. The calculated electric quadrupole moment is (2.94±0.07)ea02, where a0 is the Bohr radius and e the electronic charge while the measured value is (2.6±0.3)ea02. This is so far the most accurate determination of the electric quadrupole moment for the above mentioned state. We have also calculated the electric quadrupole moments for the metastable 4dD3/22 state of Sr+88 and for the 3dD3/2,5/22 and 5dD3/2,5/22 states of Ca+43 and Ba+138, respectively.